The ACMI & Wet-Lease Knowledge Hub.
Insights and strategy for airline executives. A neutral, plain-English resource on ACMI and wet-lease aircraft leasing: what it is, how it compares to dry leasing and ownership, what it costs, how it is regulated in Europe, and when it is the right tool.
If you plan capacity for an airline, you already know the hard part is not whether to grow. It is how to add the right aircraft, on the right route, at the right time, without locking in cost you cannot unwind. ACMI leasing exists for exactly that problem. This hub collects everything a fleet, commercial, finance or compliance team needs to evaluate it.
On this page
What ACMI leasing is
ACMI stands for Aircraft, Crew, Maintenance and Insurance: the four things a lessor provides so an airline can add a fully operational, ready-to-fly aircraft to its network in weeks rather than seasons. Because crew and operational control sit with the lessor, ACMI is a form of wet lease: the aircraft flies on the lessor's Air Operator Certificate, while the lessee (your airline) keeps the commercial side: selling the seats, setting the schedule, and carrying the brand.
The model emerged in the early 1990s as a way to match capacity to demand without the capital and lead time of buying aircraft. Today it is a mainstream fleet-planning tool: according to a Cirium 2023 survey, roughly 60% of ACMI agreements run for less than six months, reflecting its core use for seasonal peaks, route launches and fleet-gap cover.
The four components of ACMI
- AAircraft
- The lessor provides the aircraft, matched to the route and capacity you need, from regional Embraer E-Jets to narrow- and wide-bodies.
- CCrew
- Fully trained flight and cabin crew, current to ICAO and EASA standards, rostered and managed by the lessor.
- MMaintenance
- Line and base maintenance, continuing airworthiness and records, kept to the lessor's approved programme.
- IInsurance
- Hull, passenger and third-party liability, and war-risk cover, carried by the lessor for the operation.
ACMI vs wet lease, dry lease and ownership
The four routes to capacity differ most in what is bundled, how long you commit, how fast you can start, and who carries the operational risk. The table below summarises the practical differences; the full comparison article works through the numbers with European examples.
| ACMI | Wet lease | Dry lease | Ownership | |
|---|---|---|---|---|
| What's included | Aircraft + crew + maintenance + insurance | Aircraft + crew (short-term) | Aircraft only | Aircraft (yours outright) |
| Operated on whose AOC | Lessor's | Lessor's | Yours | Yours |
| Typical duration | 1–18 months (≈60% under 6) | Days to weeks | 5–10 years (≈80% over 5) | Indefinite |
| Indicative cost | ≈ €2,500–€10,000 / block hour | Premium hourly rates for urgency | ≈ €1–€7M / year + crew, maint. & insurance | ≈ €45M–€375M to acquire |
| Speed to service | ≈ 7–14 days | Days | 1–3 months | 6–12 months |
| Flexibility | High | Very high (short) | Moderate | Low |
| Operational risk to you | Low | Low | Medium | High |
| Best for | Seasonal peaks, route launches, fleet-gap cover | Urgent, ad-hoc capacity | Core fleet expansion | Stable, high-utilisation flying |
When ACMI is the right tool
ACMI is rarely an either/or against ownership. Most airlines use it alongside an owned or dry-leased core fleet. It earns its place when speed and reversibility matter more than unit cost:
- Seasonal demand. Add capacity for a summer or holiday peak and hand it back when the peak ends, with no idle aircraft in the trough.
- Route launches and market testing. Prove a route before committing capital; continue if load factors hold, walk away if they don't.
- Fleet-gap and AOG cover. Keep the schedule whole during heavy maintenance, delivery delays, or an unexpected grounding, and protect slots.
- Start-ups and fast expansion. Begin flying under an established operator's AOC while your own certification and fleet mature.
Compliance and risk in Europe
For legal and compliance teams, the central point is that an ACMI aircraft flies on the lessor's AOC, so the lessor carries the operational, crew and airworthiness responsibilities. That makes the lessor's credentials the thing to audit. In a European context the checklist usually includes a valid EASA / national-authority AOC, a functioning Safety Management System (SMS), continuing-airworthiness (CAMO) arrangements and, increasingly expected by counterparties, IOSA registration under the IATA Operational Safety Audit. Carbon-cost exposure (EU ETS / CORSIA) and slot rules also shape the economics of a given programme.
How Marathon fits
Marathon Airlines is an IOSA-registered, EASA/HCAA-certified Embraer E-Jet operator. Our compliance file (AOC, IOSA registration, SMS and records) is ready for your safety team from day one. See our credentials →
What the ACMI leasing blog covers
Each blog post addresses a high-priority question raised by airline executives when evaluating ACMI leasing options. The series is structured into five key content pillars, covering:
Definitions, comparisons, and leasing models
Pricing structures, contractual considerations, and cost factors
Operational integration, crew, maintenance, and compliance
Regulatory and legal frameworks applicable to ACMI in Europe
Strategic use cases, sustainability, and long-term fleet alignment
Each article includes aircraft category comparisons covering regional jets (Embraer E175/E190/E195), narrow-bodies (Boeing 737 / Airbus A320) and wide-bodies (Boeing 777 / Airbus A330), to help you assess the suitability of different aircraft types for each scenario.
All content is grounded in verified industry data and reflects current European market conditions.
Who should read it
- Airline executives overseeing fleet planning and procurement.
- Operational and OCC managers involved in route and capacity management.
- Legal and compliance officers evaluating contract risk and regulatory fit.
- Finance teams analysing cost models and ROI on leased aircraft.
- Commercial teams assessing route flexibility and rapid deployment needs.
In-depth articles
What is ACMI aircraft leasing, and how does it differ from other types?
The plain-English primer: what ACMI includes, how it compares to wet and dry leasing, and the real-world scenarios where it wins.
Read the article → ComparisonHow does ACMI leasing compare to owning or dry leasing aircraft?
Cost, speed, flexibility, control and risk, compared side by side, with worked European route examples.
Read the article →Frequently asked questions
What does ACMI stand for?
ACMI stands for Aircraft, Crew, Maintenance and Insurance. The lessor supplies all four, and the aircraft is operated on the lessor's Air Operator Certificate; the lessee sells the seats and controls the commercial schedule.
Is ACMI the same as wet leasing?
ACMI is a form of wet lease. In everyday use, "ACMI" tends to describe structured programmes of several weeks to many months, while "wet lease" is often used for very short-term, ad-hoc cover of days to weeks. Both bundle aircraft and crew.
How is ACMI different from dry leasing?
A dry lease is the aircraft only. You provide your own crew, maintenance and insurance and fly it on your own AOC, usually for 5–10 years. ACMI bundles crew, maintenance and insurance and is flown on the lessor's AOC, usually for 1–18 months.
How much does ACMI leasing cost?
ACMI is normally priced per block hour against a monthly minimum-hour guarantee. Indicative rates run from about €2,500 per hour for a regional Embraer E-Jet up to roughly €10,000 per hour for a wide-body, depending on type, sector length and season.
How quickly can an ACMI aircraft start flying?
Typically within about 7–14 days, compared with 1–3 months for a dry lease and 6–12 months to order and take delivery of a purchased aircraft.
Do I keep my brand and schedule on an ACMI aircraft?
Yes. The commercial side stays with you: schedule, pricing and, where practical, branding and cabin service standard, while the lessor operates the aircraft to your requirements.
Considering ACMI for next season?
Tell us the route and the dates, and we'll come back with aircraft options and indicative ACMI terms.
Contact usThis hub is an educational resource and is updated over time. For tailored advice on a specific programme, contact our team.