ACMI vs CMI: What Actually Changes in the Contract
ACMI and CMI are often treated as synonyms. They are not. The aircraft, operational control, maintenance scope and pricing all move when you switch structures.
The Aircraft Is the Only Thing That Changes, and It Changes Everything
ACMI and CMI are used interchangeably in most aviation conversations, and that is a mistake. The two letters that differ are the first one, and they change who supplies the aircraft. Everything else in the contract follows from that single decision: who holds operational control, who carries the maintenance risk, what the block-hour rate actually includes, and which regulator oversees the flying.
This page explains what actually changes when an airline or an asset owner moves between ACMI and CMI, where the boundary sits in practice, and how to decide which structure fits a given requirement. For the broader lease taxonomy, see our guide to types of aircraft leasing structures.
The one-line definition, and why it misleads
ACMI stands for Aircraft, Crew, Maintenance and Insurance. The lessor provides all four as a package, and the lessee pays fuel, airport charges, handling and the other operating costs. It is the structure most people mean when they say "wet lease."
CMI stands for Crew, Maintenance and Insurance. The aircraft is not in the package. The customer provides it, either because it owns the aircraft, because it dry leases it from a lessor, or because it has acquired it for a specific network and wants someone else to operate it.
On paper, that is a clean split. In practice, the line between the two structures blurs because the acronym describes what is supplied, not who is in control. A CMI contract in which the provider supplies crew, line maintenance, dispatch and scheduling can leave the provider as the de facto operator even though the customer owns the aircraft. An ACMI contract in which the lessee directs the schedule and controls dispatch can leave the lessee with more operational influence than the acronym suggests. For why that matters regulatorily, see our guide to operational control in aviation.
The variants most buyers never see explained
ACMI and CMI are the two structures that appear in most procurement conversations, but they sit inside a wider set of acronyms that describe exactly which services are being outsourced. The capitalisation is not decorative; it signals which element is present and which is absent.
Beyond these sits charter, where the provider supplies everything including fuel and handling for an all-inclusive price. The progression from dry lease to charter is a progression in how much of the operation is outsourced, and ACMI and CMI sit in the middle of it. Our guide to wet lease versus dry lease covers the ends of that spectrum.
What actually changes when the customer brings the aircraft
Five things move when the aircraft comes out of the package. Each one has a commercial and a regulatory consequence, and buyers who focus only on the block-hour rate miss most of them.
| Dimension | ACMI | CMI |
|---|---|---|
| Aircraft supply | Lessor provides the aircraft as part of the package | Customer provides the aircraft, usually through ownership or a separate dry lease |
| Operational control | Usually sits with the lessor, but is determined by the allocation of crew, maintenance, dispatch and scheduling rather than the label | Can sit with either party, and frequently sits with the provider even though the customer owns the asset |
| Maintenance scope | Full maintenance programme, including heavy checks and engine shop visits, funded through the block-hour rate | Typically line maintenance only. The customer retains heavy checks, engine shop visits and major component responsibility |
| Insurance | Lessor insures hull and liability as part of the package | Provider typically insures hull and liability, but the customer's asset is exposed and back-to-back coverage needs to be checked |
| Block-hour rate | Includes aircraft amortisation, so the rate is higher | Excludes aircraft cost, so the rate is lower, but the customer carries the aircraft rental or ownership cost separately |
| Typical term | Shorter, from a single season to a few years | Longer, because the customer has already committed to the aircraft |
| Exit | Lessor takes the aircraft back | Provider withdraws crew and maintenance; the customer is left with an aircraft to redeploy or redeliver |
The maintenance line is the one buyers underestimate most often. In an ACMI contract, the block-hour rate is priced to absorb the aircraft's maintenance burden, including the heavy checks that fall due during the lease. In a CMI contract, the provider typically covers line maintenance between flights, while the customer retains responsibility for the maintenance events that drive the largest cash outflows. Our guide to aircraft maintenance reserves explains why that allocation matters more than the headline rate.
Why CMI is not automatically a wet lease
The regulatory treatment follows the aircraft, not the acronym. A wet lease is generally understood as an arrangement in which the lessor provides an aircraft and at least one crew member, with the lessor retaining operational control. An ACMI contract fits that definition. A CMI contract often does not, because the customer provides the aircraft.
That distinction has three practical consequences.
Operational control is assessed, not assumed. Under 14 CFR 119.53, when a wet lease is filed with the FAA, the Administrator determines which party has operational control and issues operations specifications amendments to each party as needed, weighing crew and training, airworthiness and maintenance, dispatch, servicing and scheduling. A CMI structure in which the provider supplies crew, line maintenance and dispatch can still leave the provider as the operator, even though the customer owns the aircraft.
Wet-lease duration limits may not apply. EASA limits wet-lease-in arrangements for EU carriers to a defined period absent an exemption. A structure that is not a wet lease in the regulatory sense is not caught by that limit, which is one reason asset owners sometimes prefer CMI when they intend to keep an aircraft deployed for longer than the wet-lease window allows. For the EU and UK framework, see our guide to wet-lease regulations in the EU and UK.
Cabotage follows the operator. Neither structure solves cabotage. Traffic rights attach to the operating carrier, not to the asset owner, so a customer that owns the aircraft but does not hold the operating authority cannot use CMI to create rights it does not have. Our explainer on cabotage in aviation covers the boundary.
The corollary is that a buyer should never select CMI purely to escape a wet-lease rule. The structure has to match the actual allocation of control, or the regulator will recharacterise it. Our guide to air operator certificate explains why the AOC holder, not the asset owner, is the reference point for most of these questions.
Where CMI makes commercial sense
CMI is not a niche structure. It is the operating model behind several of the largest freighter networks in the world, and it exists because asset ownership and operating capability are genuinely separate businesses.
The common thread is that the customer wants control of the asset and the schedule, but not the operating organisation. CMI lets it keep the aircraft on its own balance sheet while buying the capability it does not have. Atlas Air describes its CMI product as an option for ramping up operations quickly, with the customer benefiting from flight crews, crew resourcing, maintenance presence and dispatch without acquiring an aircraft through the provider.
Where ACMI makes commercial sense
ACMI is the better fit when the requirement is capacity rather than asset control. The buyer wants a flying aircraft on a defined network for a defined period, and does not want to own, lease or maintain the asset itself.
- Seasonal capacity: a leisure carrier adding summer flying without a permanent fleet increase.
- Route launches: testing a city pair before committing to a dry lease or an order.
- Delivery gaps: covering a schedule while new aircraft are delayed. For the market context, see why airlines are turning to ACMI in 2026.
- Groundings: replacing capacity when an owned aircraft is out of service for maintenance or engine work.
- Single-contract simplicity: one provider, one rate, one point of accountability for everything except fuel and airport charges.
The trade-off is cost and control. ACMI carries a higher block-hour rate because the aircraft is in the package, and the lessee has less influence over the asset than a customer that owns it. For buyers weighing ACMI against other capacity structures, our guides to damp lease versus wet lease versus ACMI and aircraft damp leasing cover the adjacent options.
The pricing difference, stated properly
Comparing an ACMI block-hour rate with a CMI block-hour rate directly will always make CMI look cheaper, because the aircraft is not in the rate. That comparison is meaningless unless the aircraft cost is added back on the CMI side.
A proper comparison has three lines:
| Cost line | ACMI | CMI |
|---|---|---|
| Aircraft cost | Inside the block-hour rate | Separate: ownership cost or dry-lease rental, paid by the customer |
| Operating services | Inside the block-hour rate | Inside the block-hour rate |
| Heavy maintenance | Inside the block-hour rate, funded through reserves | Typically the customer's responsibility, beyond line maintenance |
Once the aircraft cost and the heavy maintenance exposure are added to the CMI side, the gap narrows considerably, and in some cases reverses. For how block-hour pricing is constructed, see our guide to ACMI lease pricing explained and our explainer on block time in aviation.
What to ask before choosing between them
Decision checklist
- Do you want to own or control the asset? If yes, CMI is the structural starting point. If no, ACMI is simpler.
- Who will hold operational control, and can you evidence it? Map crew, dispatch, maintenance control and scheduling before drafting. The label will not settle it, and the regulator will look through it.
- Who carries heavy maintenance and engine shop visits? In CMI these usually sit with the customer. Price them in before comparing rates.
- What is the intended lease duration? If the programme is likely to run beyond the wet-lease window in the relevant jurisdiction, CMI may be the cleaner structure, provided the control allocation supports it.
- Does either structure change your traffic-rights position? Neither creates rights the operator does not hold. Confirm the operating carrier's authority before committing to a structure.
- What happens at exit? On ACMI, the lessor takes the aircraft back. On CMI, the customer is left with an asset to redeploy, redeliver or sell. Our guide to aircraft redelivery conditions covers the exit economics.
- Is the insurance back-to-back? In CMI the customer owns the asset, so the hull and liability cover supplied by the provider must align with the customer's own policies and lender requirements.
- Which clauses actually shift between the two? Substitution rights, maintenance reserves, delay remedies and early termination all behave differently. Our guide to ACMI contract clauses airlines should negotiate sets out the terms that matter.
If you are preparing a formal requirement, our guides to ACMI RFP data points airlines should provide and how to structure an ACMI RFP apply to both structures, with the aircraft line removed on the CMI side. For the provider landscape, see our ranking of cargo ACMI providers.
Final view
The difference between ACMI and CMI is not a difference in service quality or provider sophistication. It is a difference in who supplies the asset, and that single decision cascades into operational control, maintenance exposure, insurance structure, pricing and regulatory treatment.
Buyers who treat the two as interchangeable tend to discover the difference at the point where it is most expensive: when a heavy check falls due and nobody budgeted for it, when a regulator decides the customer is the operator and the customer disagrees, or when a lease ends and the customer is left holding an aircraft it has no plan for. Buyers who decide the asset question first, and draft the contract around the control determination second, avoid most of that.
Structuring an ACMI or CMI programme?
Whether the requirement is a full ACMI package or a CMI arrangement around an aircraft you already control, matching the structure to the mission and the regulatory position is the first decision. For aircraft leasing and sourcing enquiries, visit Blue Cube Aviation.
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