Knowledge
What is ACMI / wet lease?
ACMI stands for Aircraft, Crew, Maintenance and Insurance. In a wet lease, an airline provides the aircraft plus these four elements to the lessee, who pays for fuel, airport charges, permits and handling under the agreed commercial split.
ACMI is a lease in which the lessor supplies the aircraft, crew, maintenance and insurance against guaranteed monthly block hours, while the lessee pays fuel, airport, ATC, handling and permits and controls the commercial network.
What ACMI covers
The lessor supplies the aircraft, the flight crew, all maintenance including line and base checks, and hull and liability insurance. The aircraft normally operates under the lessor's Air Operator Certificate, which means the lessor retains operational control and safety responsibility.
Commercially the contract is built on guaranteed monthly block hours, typically in the range of 200 to 350 hours per month for a freighter programme, with an hourly rate that falls as guaranteed volume rises. Hours flown below the guarantee are still paid for, which is why realistic network planning matters before signing.
What the lessee covers
Fuel, airport and navigation charges, ATC, ground handling, de-icing, overflight and landing permits, crew accommodation and per diems in many contracts, and the commercial risk of filling the aircraft.
The lessee also owns the traffic rights and the customer relationship. In practice this is why airlines, integrators and large forwarders use ACMI: they keep the network and the revenue and buy only the flying.
Wet, damp and dry lease
Wet lease is the full ACMI package. Damp lease usually means aircraft, maintenance and insurance plus flight crew, with the lessee supplying cabin crew, which is more relevant to passenger operations than to freighters. Dry lease is the aircraft alone: the lessee provides crew, maintenance and insurance and operates under its own AOC.
Dry lease is a financing and fleet decision with a long lead time and heavy regulatory work. ACMI is an operational decision that can be executed in weeks.
When ACMI is the right structure
Seasonal peaks such as flower and perishables seasons or Q4 e-commerce. Fleet gaps caused by heavy maintenance, delayed deliveries or an unserviceable aircraft. Route trials where an airline wants to prove a lane before committing capital. Rapid capacity growth where aircraft acquisition would take too long.
Below roughly one flight per week over a short period, ad-hoc charter is usually cheaper and simpler. Above a few flights per week sustained over months, ACMI generally wins on hourly cost and reliability.
Structuring the programme
The requirement that gets sourced properly specifies: aircraft type or category and required payload, route or network and sector lengths, start date and duration, guaranteed monthly block hours, frequency, crew base and positioning, handling responsibilities, the fuel, ATC and airport assumptions, and the regulatory context in every jurisdiction on the network.
Regulatory scope decides feasibility as much as price. Foreign wet lease into and within the EU requires authority approval, and several jurisdictions restrict duration, cabotage and third-country operators. Approvals take time and must be built into the start date.
Contract terms to watch
Minimum guaranteed hours and how unused hours are treated, the definition of a block hour, rate escalation and fuel or currency clauses, maintenance and AOG substitution obligations, delay and cancellation regimes, insurance limits, security deposits, and termination and redelivery conditions.
These clauses, not the headline hourly rate, decide what the programme actually costs over a season.
How long can an ACMI run?+
From short-term seasonal peaks of a few weeks to multi-year programmes, subject to the regulatory scope and approval duration limits in each operating jurisdiction.
Who has operational control in a wet lease?+
The lessor. The aircraft operates on the lessor's AOC with the lessor's crew and maintenance, and the lessor carries operational and safety responsibility.
What is the difference between ACMI and charter?+
Charter is priced per flight or per rotation for a defined mission. ACMI is priced per block hour against a guaranteed monthly volume over a period, with the lessee controlling the network.
How are ACMI rates quoted?+
As an hourly block-hour rate against guaranteed minimum monthly hours, plus positioning, and excluding fuel, airport, ATC, handling and permits, which the lessee pays.
More answers in the FAQ hub with 50+ questions.
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