The Aircraft, Crew, Maintenance, and Insurance (ACMI) lease is a comprehensive arrangement in commercial aviation, often called a “Wet Lease.” This package allows an airline to rapidly acquire an airworthy aircraft and the necessary personnel to operate it on its routes. ACMI is a powerful tool for short-to-medium-term capacity management, enabling quick responses to market demands or unexpected fleet shortages.
Defining ACMI and Its Components
ACMI represents the four core elements the lessor provides to the lessee, establishing a complete, ready-to-fly operation. The “Aircraft” component means the lessor supplies a fully airworthy airplane. It remains on the lessor’s Air Operator Certificate (AOC) and registration, ensuring compliance with all regulatory standards and suitability for immediate commercial service.
The “Crew” element includes the cockpit crew (pilots and first officers) and the cabin crew. The lessor handles all crew logistics, including training, rostering, accommodation, and salary payments, ensuring personnel are qualified for the specific aircraft type. “Maintenance” covers both line maintenance (routine checks) and heavy maintenance (major inspections and overhauls). The lessor manages the maintenance schedule, spare parts, and associated costs to guarantee continuous airworthiness.
Finally, “Insurance” stipulates that the lessor holds the necessary hull insurance for the aircraft and liability insurance. This protects the aircraft’s value and covers third-party claims, transferring this financial risk away from the lessee. The provision of all four elements defines the comprehensive ACMI structure, often referred to as a Wet Lease.
Distinguishing ACMI from Other Aviation Leases
The aviation industry uses various leasing models, differentiated by which operational components the lessor provides. ACMI is the most comprehensive operational lease, delivering a full package (A, C, M, I) that offers a turnkey flight solution. This arrangement allows the lessee to focus solely on commercial aspects, such as ticket sales and branding.
A Dry Lease, conversely, is the most basic arrangement, where the lessor provides only the “Aircraft.” The lessee assumes full responsibility for the Crew, Maintenance, and Insurance, integrating the aircraft into its own fleet and operating it under its own AOC. Dry leases typically span a longer duration, often five to ten years, reflecting a long-term commitment.
A Damp Lease is a hybrid model, falling between a Dry Lease and a full ACMI Wet Lease. The lessor provides the Aircraft, Maintenance, Insurance, and the Cockpit Crew. The lessee is responsible for providing its own Cabin Crew. This hybrid is often chosen by airlines seeking to maintain control over the passenger experience and service standards.
Strategic Reasons for Utilizing ACMI Agreements
Airlines use ACMI agreements to address sudden or temporary capacity fluctuations without the expense of permanent fleet expansion. A primary strategic driver is covering seasonal demand peaks, such as the busy summer holiday period or specific religious travel seasons. Leasing an aircraft for a few months allows the airline to maximize revenue during these high-traffic windows.
ACMI also serves as a rapid response solution when an airline’s owned aircraft are unexpectedly grounded (Aircraft on Ground or AOG). Quickly obtaining a fully operational replacement aircraft maintains schedule integrity and minimizes passenger disruption. This arrangement also provides a low-risk method for testing a new route or market before committing to a long-term investment. The flexibility of an ACMI contract allows an airline to determine the viability of network expansion with minimal upfront capital expenditure.
The Operational Structure of an ACMI Lease
While the lessor manages the fixed operational elements, the lessee is responsible for all variable costs associated with operating the flight. The most significant financial responsibility is the cost of fuel, which fluctuates based on global market prices and route length. The lessee also covers all airport-specific charges, including landing fees, navigation fees, and passenger handling expenses.
Other financial obligations involve catering, ground handling services, and government taxes or duties. The ACMI payment structure is two-tiered: a fixed monthly fee covering the lessor’s costs (A, C, M, I), and a variable hourly rate. This variable rate is calculated based on “block hours” flown—the time from when the aircraft moves under its own power until it stops at the destination gate—ensuring payment only for active utilization.
Key Advantages and Disadvantages of ACMI
A major advantage of ACMI is the immediate scalability and speed of deployment, allowing a carrier to add capacity within weeks. This arrangement substantially reduces capital expenditure (CAPEX) for the lessee, as the financial burden of maintenance reserves and aircraft acquisition is absorbed by the lessor. The lessor’s retention of maintenance and insurance responsibilities also reduces the lessee’s exposure to unforeseen operational and financial risks.
However, ACMI arrangements come with trade-offs. The most significant is the higher hourly operating cost compared to an owned or dry-leased aircraft, reflecting the comprehensive service and flexibility provided. Furthermore, the lessee has less control over the on-board product, as the crew are employed by the lessor and may wear the lessor’s uniform, potentially diluting the lessee’s brand experience. Operational integration can also present a challenge, requiring the lessor’s aircraft and crew to integrate seamlessly with the lessee’s systems and scheduling.