Wet Lease, Dry Lease and ACMI Agreements: Why Do Airlines Lease Aircraft and Crew from Other Companies?

1. Introduction

Especially during the summer months, passengers travelling from busy airports such as Istanbul, Antalya, Izmir, Bodrum and Dalaman may encounter an interesting situation: the ticket has been purchased from one airline, yet the aircraft may carry the livery of another airline, the pilots and cabin crew may wear different uniforms, and the aircraft may even be registered in a foreign country.

This does not necessarily indicate an unusual or unlawful operation. On the contrary, wet lease, dry lease and ACMI agreements are among the principal commercial tools used by modern airlines to manage fleet capacity.

For example, a Turkish airline may experience a rapid increase in demand on Antalya–London, Istanbul–Berlin or Izmir–Amsterdam routes during the summer season. Its existing fleet may not be sufficient to meet such demand. Purchasing a new Airbus A321neo or Boeing 737 MAX not only requires substantial financing but may also involve delivery lead times of several years. By contrast, leasing capacity from another airline together with aircraft, pilots, cabin crew, maintenance and insurance may provide a practical solution for a temporary need lasting only a few months.

Among the contractual models used for this purpose, the most important are wet lease, dry lease, and what is commonly referred to in the industry as ACMI – Aircraft, Crew, Maintenance and Insurance.

However, these agreements cannot be treated as ordinary movable property leases. They raise a series of distinct legal questions, including:

• Under whose Air Operator Certificate – AOC the aircraft is operated;
• Which company employs and controls the pilots;
• Who exercises operational control over the flight;
• Who is responsible for maintenance and continuing airworthiness;
• Which airline is liable vis-à-vis passengers;
• Which insurance policy responds in the event of an accident.

In Türkiye, one of the principal regulatory instruments governing these matters is the Instruction on the Procedures and Principles Regarding Aircraft Leasing – SHT-KİRALAMA, issued by the Turkish Directorate General of Civil Aviation (“DGCA” or “SHGM”). According to the current SHGM regulatory index, the Instruction was published on 1 November 2024 and most recently amended on 6 May 2026.

Accordingly, the key to understanding wet lease and dry lease arrangements is not merely the question:

“Who leased the aircraft?”

The more important legal question is:

“Who has legal and operational control over the aircraft?”

2. What Is the Fundamental Difference Between Wet Lease and Dry Lease?

In international aviation law, one of the most important criteria for distinguishing different leasing structures is the AOC under which the aircraft is operated.

Under the Turkish SHT-KİRALAMA framework, a dry lease is an arrangement in which the aircraft is operated under the operating licence and AOC of the lessee, whereas a wet lease is an arrangement in which the aircraft continues to be operated under the operating licence and AOC of the lessor.

A similar approach applies under European aviation law. Under EU regulations, a dry lease generally refers to an aircraft operated under the lessee’s AOC, while a wet lease refers to an aircraft operated under the lessor’s AOC.

Therefore, the title of the agreement itself is not decisive. Simply calling a contract a “Wet Lease Agreement” or an “Aircraft Lease Agreement” does not determine its true legal nature. The actual operational structure must be examined.

A dry lease is therefore economically closer to a conventional aircraft lease.

A wet lease, by contrast, is not merely the provision of an aircraft. It is more accurately described as the procurement of operational airline capacity from another air operator.

3. What Is ACMI? Is It the Same as Wet Lease?

The term ACMI consists of the initials of four words:

Aircraft – Crew – Maintenance – Insurance.

In a conventional ACMI arrangement, the service provider supplies the aircraft, flight crew, maintenance organisation and insurance together.

For this reason, ACMI and wet lease are often used interchangeably in commercial practice.

However, from a legal perspective, a subtle but important distinction should be made.

Wet lease is principally a regulatory and operational classification, whereas ACMI describes the commercial scope of the services supplied under the agreement.

Under Turkish aviation regulations, the legal definition of a wet lease does not depend solely on whether all four ACMI elements are supplied by the lessor. The defining factor is that the aircraft is operated under the operating licence and AOC of the lessor.

Therefore, although an ACMI arrangement will usually constitute a wet lease, the legal characterisation of the transaction should not be determined merely by the word “ACMI” appearing in the title of the contract.

International practice also recognises intermediate models such as damp lease arrangements.

A damp lease generally describes a structure in which, for example, the aircraft and cockpit crew are provided by the lessor while the cabin crew is supplied by the lessee. In European and UK aviation practice, this is commonly treated as a partial wet lease arrangement.

4. Why Do Airlines Use Wet Lease or ACMI Arrangements?

At first sight, leasing an aircraft together with crew and operational support from another airline may appear expensive. Nevertheless, the ACMI market becomes particularly active during peak travel seasons.

The main reason is that airline capacity requirements are not constant throughout the year.

Seasonal Passenger Demand

Türkiye provides a particularly clear example.

Between June and September, demand for European flights from Antalya, Dalaman, Bodrum and Izmir may increase dramatically, whereas the same level of capacity may not be needed during the winter season.

Purchasing an aircraft worth tens or even hundreds of millions of dollars simply to use it for four months each year may not be economically rational.

An ACMI agreement allows the airline to obtain temporary capacity during the peak season.

EU legislation itself expressly recognises seasonal capacity needs as one of the circumstances in which the wet leasing of third-country registered aircraft may be justified. Regulation (EC) No 1008/2008 also recognises exceptional needs and operational difficulties as legitimate grounds for wet leasing.

Unexpected Aircraft Grounding

An aircraft may become unavailable for several weeks due to engine failure, bird strike, structural damage, heavy maintenance or another technical issue.

In aviation terminology, such circumstances are often referred to as Aircraft on Ground – AOG.

The cost of an aircraft being grounded is not limited to the repair bill.

An airline may also face:

• flight cancellations,
• passenger re-routing,
• accommodation expenses,
• passenger compensation,
• loss of slots,
• network disruption,
• reputational damage.

For this reason, an airline may lease an ACMI aircraft for several weeks or months in order to maintain its schedule.

Opening a New Route

An airline may wish to test market demand before committing permanent aircraft capacity to a new destination.

For example, it may consider launching a new route from Istanbul to an African destination or introducing seasonal flights between Antalya and Scandinavia.

Instead of making a permanent fleet investment, the airline may test the commercial viability of the route using ACMI capacity.

Delays in Aircraft Deliveries

Delays in Airbus or Boeing production and deliveries may have a direct impact on fleet planning.

An airline may schedule its summer programme on the assumption that new aircraft will be delivered in April, only to be informed that delivery has been postponed until September.

The resulting capacity gap can be covered through an ACMI lease.

Pilot or Cabin Crew Shortages

An airline may have sufficient aircraft but insufficient numbers of pilots holding the necessary type rating or insufficient cabin crew.

Wet lease arrangements provide not only an aircraft but also a ready-to-operate aviation organisation.

Hajj, Umrah, Sports Events and Major Organisations

Very significant passenger movements may arise within short periods.

Examples include:

• Hajj and Umrah operations,
• UEFA and FIFA events,
• Olympic Games,
• major congresses,
• seasonal charter programmes operated by tour operators.

For such operations, temporary ACMI capacity may be commercially more efficient than permanently expanding the fleet.

5. Legal Framework for Wet Lease and Dry Lease in Türkiye

Aircraft leasing transactions under Turkish law cannot be analysed solely as lease agreements under the Turkish Code of Obligations.

Commercial air transport is subject to extensive regulatory supervision.

Accordingly, the following instruments must be considered together:

• Turkish Civil Aviation Act No. 2920;
• Regulation on Commercial Air Transport Operators – SHY-6A;
• SHT-KİRALAMA;
• SHT-OPS;
• regulations relating to continuing airworthiness;
• aviation insurance legislation; and
• international aviation conventions to which Türkiye is a party.

SHT-KİRALAMA regulates the principles governing the leasing and subleasing of aircraft by commercial air transport operators for passenger and cargo operations.

The Instruction permits wet leases, short-term wet leases and dry leases between Turkish and foreign operators subject to the applicable conditions.

6. What Is a “Short-Term Wet Lease” in Türkiye?

One of the notable concepts under the current SHT-KİRALAMA framework is the short-term wet lease.

Under the Instruction, a short-term wet lease refers to a wet lease operation of up to 72 total flight hours within any calendar month, subject to compliance with flight and duty time limitations and rest requirements.

This mechanism can be particularly useful in cases involving:

• short-term technical failures,
• exceptionally busy weekends,
• charter operations,
• temporary capacity shortages affecting only a limited number of flights.

7. Can Two Turkish Airlines Enter into a Wet Lease?

Yes.

Under the current regulatory framework, wet lease arrangements may be concluded between two Turkish air operators.

Moreover, under SHT-KİRALAMA, wet lease operations between two domestic operators may, provided that the applicable conditions are satisfied, be implemented without obtaining a separate individual wet lease approval from SHGM.

Nevertheless, this does not mean that such operations are exempt from regulatory supervision.

In order for SHGM to monitor the operations, wet lease operations conducted during the preceding month must be reported to the authority by the tenth day of each calendar month.

Accordingly, the fact that “prior approval is not required” should not be interpreted as meaning that the operation falls outside the regulatory framework.

Requirements relating to:

• operating licences,
• airworthiness,
• insurance,
• operational safety,
• crew licensing,
• applicable aviation legislation,

continue to apply.

8. Can a Turkish Airline Wet Lease an Aircraft from a Foreign Airline?

Yes.

However, wet leasing from a foreign operator is subject to stricter conditions.

Under the current SHT-KİRALAMA framework, where a Turkish operator intends to wet lease an aircraft from a foreign operator, an application must normally be submitted to SHGM at least 15 days before the planned commencement of the operation and approval must be obtained.

An approval granted by SHGM for such a foreign wet lease may be issued for a maximum period of eight months at a time.

The foreign lessor must hold a valid operating licence and must be licensed by an ICAO Contracting State.

The current Instruction also imposes detailed safety-related requirements concerning matters such as:

• SAFA performance,
• IOSA registration,
• EASA operating approvals,
• EASA TCO authorisation,
• ICAO safety oversight performance of the relevant state.

The purpose of these requirements is not merely to regulate economic competition.

The fundamental concern is whether an aircraft registered abroad and operated under a foreign AOC can provide a level of aviation safety equivalent to the standards required for Turkish-related commercial operations.

9. Can a Foreign Wet-Leased Aircraft Be Used on Domestic Routes in Türkiye?

This question is particularly important under Turkish aviation law because of cabotage rules.

Under the current SHT-KİRALAMA framework and Article 31 of the Turkish Civil Aviation Act No. 2920, foreign wet-leased aircraft with a capacity of 100 seats or more, or aircraft configured solely for cargo transport, may under certain conditions be used for commercial transportation between two points within Türkiye.

However, the regulation adopts the principle that the operator should first seek aircraft from domestic operators.

Where foreign capacity is used, the Turkish lessee may be required to demonstrate to SHGM, through records or reports, that the capacity need could not reasonably or practically be satisfied through domestic operators.

Specific nationality requirements may also apply to cabin crew used on foreign wet-leased aircraft operating domestic sectors.

Under the current rules, the majority of the minimum cabin crew complement and the senior cabin crew member must generally be Turkish citizens, subject to specific exceptions including provisions concerning Blue Card holders.

This demonstrates that wet lease transactions are not merely private law agreements.

They also interact directly with:

• Turkish aviation policy,
• cabotage rules,
• labour considerations,
• domestic aviation market protection.

10. Who Has Operational Control in a Wet Lease?

This is one of the most important legal consequences of a wet lease structure.

Under SHT-KİRALAMA, responsibility for:

• continuing airworthiness,
• flight operations,
• other administrative and operational obligations

generally remains with the lessor, while commercial responsibility generally remains with the lessee.

The allocation of these responsibilities must be expressly reflected in the lease agreement.

In the case of a wet lease from a foreign operator, the distinction becomes even more explicit.

The foreign lessor generally remains responsible for:

• operation of the aircraft;
• training and qualification of flight and cabin crew;
• operational control;
• dispatch and flight following;
• crew scheduling;
• aircraft maintenance;
• continuing airworthiness management.

The Turkish lessee, by contrast, assumes the commercial side of the operation.

This distinction is extremely important.

For example, the Istanbul–Antalya flight may be sold by Airline A, while the aircraft is actually operated under a wet lease by Airline B.

Airline A may manage:

• ticket sales,
• pricing,
• commercial scheduling,
• customer relations,
• marketed capacity.

However, Airline A may not have authority to:

• give operational instructions to Airline B’s pilots;
• determine whether the aircraft is technically fit to fly;
• interfere with the captain’s operational decisions;
• manage the technical operation of the aircraft.

Those functions remain within Airline B’s operational organisation.

11. “Aircraft” Obligations under an ACMI Agreement

The ACMI provider must first make available an aircraft meeting the type and configuration requirements agreed under the contract.

This apparently simple obligation may become one of the most heavily disputed parts of the agreement.

Merely describing the aircraft as an “Airbus A320” will often be insufficient.

The contract should address matters such as:

• aircraft type and variant;
• manufacturer serial number;
• registration;
• aircraft age;
• seating capacity;
• cabin configuration;
• ETOPS capability;
• MEL status;
• performance characteristics;
• noise certification;
• airworthiness documentation;
• required operational approvals.

The agreement should also determine whether the lessor is obliged to provide a substitute aircraft where the designated aircraft becomes technically unavailable.

The commercial risk for the lessee can be significant.

For example, an airline may have planned its capacity based on a 200-seat A321, but due to a technical issue the lessor may offer a 180-seat A320 instead.

The agreement should therefore determine:

• which passengers may have to be offloaded;
• who bears the resulting revenue loss;
• whether passenger compensation is recoverable;
• how the block-hour charges will be recalculated.

12. “Crew” – Who Is Responsible for Pilots and Cabin Crew?

Under a conventional ACMI arrangement, the pilots and cabin crew are normally supplied by the lessor.

Those personnel must hold all necessary:

• licences,
• medical certificates,
• type ratings,
• recurrent training records,
• route qualifications,
• airport qualifications.

However, crew responsibility extends beyond licensing.

Other issues include:

• flight time limitations;
• duty time limitations;
• rest periods;
• accommodation;
• crew positioning;
• visas;
• work permits;
• airport access permissions.

For example, if a foreign ACMI operator bases an aircraft in Antalya for three months, the agreement should address:

• entry into Türkiye by foreign crew;
• accommodation arrangements;
• airport security passes;
• crew transportation;
• local operational training requirements.

SHT-KİRALAMA also requires operators to ensure that the necessary physical conditions and training requirements are satisfied in relation to the operational base and airports from which wet lease operations will be conducted.

13. “Maintenance” – Who Is Responsible for Aircraft Maintenance?

Maintenance is one of the core obligations of an ACMI provider.

Leasing the aircraft does not relieve the lessor of its technical responsibilities.

Since operational responsibility in a wet lease remains primarily with the lessor, continuing airworthiness and maintenance management also generally remain within the lessor’s area of responsibility.

Under the Turkish regulatory framework, maintenance and maintenance management of foreign wet-leased aircraft must be performed through organisations recognised by the relevant state of registration authority.

However, the contract may separately allocate the economic burden of different maintenance-related costs.

For example:

• routine line maintenance may be borne by the lessor;
• damage caused by the lessee’s ground handling contractor may be charged to the lessee;
• foreign object damage may be allocated depending on fault;
• extraordinary maintenance may be dealt with under a separate cost-sharing mechanism.

Accordingly, the phrase “maintenance included” should not automatically be interpreted as meaning that the lessor bears every maintenance-related expense without exception.

14. “Insurance” – Who Arranges Insurance?

The final letter of ACMI, “I”, stands for Insurance.

Aviation insurance is not limited to hull insurance covering the physical value of the aircraft.

Relevant coverage may also include:

• passenger liability;
• third-party liability;
• baggage liability;
• cargo liability;
• war risks;
• terrorism risks;
• crew liability;
• other operational risks.

Under Turkish wet lease regulations, the agreement must specify how insurance responsibilities are allocated between the parties.

The relevant insurance policies must also extend to the contemplated wet lease operation.

For this reason, a simple contractual provision stating:

“The lessor shall maintain insurance”

is generally insufficient.

A properly drafted ACMI agreement should also address:

• policy limits;
• scope of cover;
• additional insured status;
• waiver of subrogation;
• hull all risks;
• war risks;
• third-party liability cover;
• passenger liability insurance.

15. Which Costs Are Usually Paid by the Lessee in an ACMI Arrangement?

The fact that the four ACMI elements are supplied by the lessor does not mean that every cost associated with the flight is borne by the lessor.

In many ACMI agreements, the lessee may separately pay:

• fuel;
• airport charges;
• navigation charges;
• ground handling;
• passenger handling;
• catering;
• de-icing;
• certain crew accommodation expenses;
• crew transfers;
• other locally incurred operational costs.

The commercial relationship is frequently priced on a block-hour basis.

For example, the parties may agree on a specified US dollar or Euro rate for each block hour flown.

This raises several additional contractual questions:

What is the monthly minimum guaranteed block-hour commitment?

Must the lessee pay the minimum hours even if the aircraft does not fly?

Are positioning and ferry flights chargeable?

How are technical cancellations treated for minimum-hour calculations?

Who bears the financial consequences of slot loss?

These matters can create disputes worth millions of dollars even in ACMI arrangements lasting only a few months.

16. Wet Lease from the Passenger’s Perspective: “Which Airline Am I Actually Flying With?”

This is one of the most visible effects of wet leasing in everyday travel.

A passenger may purchase a ticket from Airline A and then arrive at the airport to discover that the flight will be operated by Airline B.

Turkish aviation regulations impose an express information obligation in this respect.

Under SHT-KİRALAMA, where a Turkish operator uses an aircraft under a wet lease or short-term wet lease from another Turkish or foreign operator, passengers must be informed of the identity of the actual operating carrier before boarding.

The responsibility for providing this information rests with the lessee.

Accordingly, the brand from which the passenger purchases the ticket may differ from the airline that actually operates the flight.

This distinction also corresponds to the concepts of:

contracting carrier and actual carrier

under international aviation law.

Article 39 of the 1999 Montreal Convention expressly recognises situations in which the person entering into the contract of carriage with the passenger is different from the person who performs all or part of the carriage.

More importantly, under Article 45 of the Montreal Convention, subject to the applicable conditions, a passenger suffering damage may bring proceedings against:

• the actual carrier;
• the contracting carrier; or
• both carriers.

Therefore, even where two airlines allocate passenger-related liability between themselves under the ACMI agreement, such internal contractual allocation does not necessarily deprive passengers of rights granted by mandatory law or international conventions.

If one carrier pays compensation to a passenger and subsequently seeks reimbursement from the other carrier under contractual indemnity or recourse provisions, that is a separate question concerning the internal relationship between the parties.

17. What Are the Most Important Clauses in a Wet Lease Agreement?

A sophisticated ACMI or wet lease agreement is not simply a short document specifying the aircraft type and daily rental rate.

One of the most important aspects of international practice is the preparation of a detailed operational responsibility matrix.

The agreement should clearly identify which party is responsible for each operational and commercial function.

Particular attention should be given to:

• aircraft availability;
• AOC responsibility;
• crew;
• training;
• maintenance;
• continuing airworthiness;
• insurance;
• fuel;
• ground handling;
• airport charges;
• navigation charges;
• catering;
• de-icing;
• passenger handling;
• baggage handling;
• slots;
• permits;
• traffic rights;
• security;
• dangerous goods;
• passenger claims;
• delay compensation;
• crew accommodation;
• visas;
• taxation.

In addition, the following clauses are particularly important in commercial disputes:

Minimum Guaranteed Block Hours

The minimum amount of flying capacity for which the lessee is obliged to pay even if the aircraft is not fully utilised.

Aircraft Availability

The minimum percentage of time during which the aircraft must remain available for operations.

AOG Provisions

The contractual mechanism applicable where the aircraft becomes unavailable due to a technical issue.

Replacement Aircraft

The lessor’s obligation, if any, to provide substitute aircraft.

Performance Standards

Service-level requirements concerning timely aircraft availability and delays attributable to the lessor.

Liquidated Damages

Pre-agreed financial consequences for specified breaches.

Indemnity

Provisions allowing one party to recover sums paid to third parties where the loss contractually belongs to the other party.

Insurance

Policy limits, scope of cover and insured status of the parties.

Force Majeure

Events such as:

• war,
• airspace closures,
• volcanic activity,
• pandemic restrictions,
• embargoes,
• other extraordinary events.

Sanctions and Export Controls

Compliance with sanctions and export-control regimes, particularly those of:

• the United States,
• European Union,
• United Kingdom.

These restrictions may affect:

• aircraft operations;
• maintenance;
• insurance;
• banking;
• payment flows.

Termination Events

Potential termination triggers may include:

• suspension of an AOC;
• expiry or cancellation of insurance;
• loss of airworthiness;
• payment default;
• sanctions designation;
• regulatory prohibition.

Governing Law and Dispute Resolution

The agreement should determine:

• applicable law;
• jurisdiction;
• arbitration institution, if any;
• seat of arbitration;
• procedural language.

18. What Happens If the AOC Is Suspended?

The AOC is fundamental to the legal structure of a wet lease.

This is because the essential feature of wet leasing is that the aircraft is operated under the lessor’s AOC.

If the lessor’s operating licence or AOC is suspended or revoked, continuation of the agreement may become legally or practically impossible.

SHT-KİRALAMA recognises circumstances such as:

• suspension of operations;
• suspension of the operating licence;
• revocation of the operating licence

as events capable of bringing a leasing arrangement to an end.

Serious safety issues or the blacklisting of a foreign operator under an applicable safety oversight regime may likewise render continued operations impossible.

For this reason, international ACMI agreements usually contain detailed regulatory termination event provisions.

19. Why Is ICAO Article 83 bis Important in Dry Lease Transactions?

A different regulatory problem arises when a dry lease has an international dimension.

The aircraft may be registered in one country while being operated under the AOC of an airline established in another country.

For example, an aircraft may remain registered in Ireland while being dry leased to and operated by a Turkish airline.

In such circumstances, the State of Registry and the State of the Operator are different.

Article 83 bis of the Chicago Convention enables certain regulatory functions and responsibilities to be transferred from the State of Registry to the State of the Operator.

ICAO describes this mechanism as a framework allowing certain responsibilities of the State of Registry to be transferred to the State of the Operator where an aircraft is operated under a lease, charter or interchange arrangement.

The current Turkish SHT-KİRALAMA framework also treats Article 83 bis arrangements as an important element of international dry leasing between Türkiye and foreign states.

Accordingly, an international dry lease is not merely a private contract between the aircraft owner and the airline.

The process may also require a regulatory responsibility transfer between the civil aviation authorities of the two states concerned.

20. Why Is Dry Lease Commonly Used for Long-Term Fleet Planning?

Wet lease arrangements are frequently used for short- or medium-term capacity needs, whereas dry lease arrangements are commonly used for long-term fleet planning and aircraft financing.

Instead of purchasing ten Airbus A321 or Boeing 737 aircraft, an airline may obtain them from aircraft leasing companies under dry lease contracts lasting eight to twelve years.

Under this structure, the airline may use:

• its own pilots;
• its own cabin crew;
• its own operational organisation;
• its own passenger service standards;
• its own branding.

From the passenger’s perspective, the aircraft will often appear to be an ordinary part of the airline’s own fleet.

Dry leasing therefore allows an airline to expand its fleet without incurring the substantial initial capital cost associated with outright aircraft ownership.

In simplified commercial terms:

wet lease is primarily a method of acquiring temporary capacity, whereas dry lease is primarily a method of acquiring aircraft for integration into the airline’s own fleet.

21. Wet Lease under European Union Law

Although Türkiye is not an EU Member State, EU wet lease rules remain commercially significant because Turkish airlines operate extensively in the European market.

Article 13 of Regulation (EC) No 1008/2008 permits EU air carriers to use dry-leased and wet-leased aircraft.

However, wet leasing an aircraft registered in a third country outside the EU is subject to stricter conditions.

In particular, where a third-country registered aircraft is wet leased, the EU carrier must demonstrate equivalent safety standards and satisfy additional regulatory conditions.

The regulation recognises justifications such as:

• exceptional needs;
• seasonal capacity requirements;
• operational difficulties.

This reflects the general policy that wet lease should function as a tool for responding to specific operational or commercial needs rather than as an unlimited mechanism allowing airlines permanently to outsource their entire operational structure.

22. How Can an ACMI Dispute Arise?

Consider a simple example.

Turkish Airline A enters into an ACMI agreement with foreign Airline B for three Airbus A320 aircraft for the period from 1 June to 30 September.

The agreement guarantees a minimum of 250 block hours per aircraft per month.

In July, one of the aircraft suffers an engine failure and remains unavailable for 18 days.

The lessor is unable to provide a replacement aircraft.

Airline A is forced to cancel 40 flights and re-accommodate hundreds of passengers on alternative services.

A single technical failure may therefore generate at least five separate legal issues:

1. Whether the aircraft availability obligation has been breached;
2. Whether minimum block-hour payments remain payable;
3. Which party must ultimately bear compensation paid to passengers;
4. Whether the lessee may claim damages for lost revenue;
5. Whether the insurer or maintenance provider may also bear responsibility.

Thus, even an ACMI agreement lasting only a few months can give rise to substantial international commercial disputes and arbitration proceedings.

23. Conclusion

Wet lease, dry lease and ACMI structures form an important but often invisible part of modern commercial aviation.

A passenger travelling from Istanbul to Antalya or from Antalya to London during the summer season may purchase a ticket from one airline and find themselves travelling on an aircraft bearing another airline’s colours and operated by a different crew.

Behind that apparently simple operational arrangement may lie a sophisticated contract worth millions of dollars.

Under a dry lease, the aircraft is generally operated under the lessee’s AOC and within the lessee’s operational organisation.

Under a wet lease, the aircraft remains operated under the lessor’s AOC, and substantial operational responsibility remains with the lessor.

ACMI, referring to Aircraft, Crew, Maintenance and Insurance, is the most common commercial service model through which wet lease capacity is supplied.

From the perspective of Turkish law, these transactions cannot be analysed solely by reference to contractual provisions agreed between the parties.

The following legal sources must be considered together:

• Turkish Civil Aviation Act No. 2920;
• SHY-6A;
• current SHT-KİRALAMA;
• SHT-OPS;
• continuing airworthiness regulations;
• aviation insurance rules;
• ICAO instruments;
• applicable international conventions.

Where foreign operators are involved, additional issues may arise regarding:

• SHGM approval;
• AOC responsibility;
• airworthiness;
• oversight by foreign aviation authorities;
• insurance;
• ICAO Article 83 bis;
• cabotage;
• passenger notification requirements.

The most important legal principle can be summarised as follows:

It is not merely ownership of the aircraft that matters; the decisive questions are under whose AOC the aircraft is operated and who exercises operational control.

Similarly, a contractual clause stating that “the lessee shall be responsible for all passenger claims” or that “the lessor shall bear all damages” will not automatically exclude mandatory liability imposed by aviation legislation or international conventions.

Accordingly, a high-value wet lease or ACMI transaction should not be negotiated solely by reference to rental rates and aircraft type.

The parties should comprehensively address:

• operational control;
• crew;
• maintenance;
• continuing airworthiness;
• insurance;
• passenger liability;
• AOG events;
• replacement aircraft;
• minimum guaranteed block hours;
• indemnities;
• regulatory approvals;
• sanctions;
• events of default;
• termination;
• dispute resolution.

For airlines, wet lease and ACMI arrangements may provide one of the fastest means of carrying hundreds of thousands of additional passengers during peak season.

However, where the agreement is inadequately drafted, a single aircraft remaining grounded for several weeks may create millions of dollars in losses, passenger claims and international disputes.

For this reason, wet lease, dry lease and ACMI arrangements should not be regarded as simple “aircraft rental” transactions.

They are multi-layered aviation contracts located at the intersection of contract law, administrative and regulatory law, international air law, insurance law and commercial risk management.