ACMI & Wet Lease

What it is

ACMI stands for Aircraft, Crew, Maintenance, Insurance — the four things the lessor provides as one bundled package, as opposed to a dry lease's aircraft-only arrangement. "Wet lease" is the more general term for the same concept (wet = with crew, dry = without, mirroring the dry-lease terminology) and the two terms are used largely interchangeably in the industry. The aircraft operates under the LESSOR's own Air Operator Certificate, not the customer airline's — the customer typically pays a rate per block hour covering the ACMI package, while separately covering costs like fuel, airport and handling fees, and other trip-specific costs itself.

Why airlines use it

ACMI/wet lease capacity solves problems that owning or dry-leasing an aircraft can't solve as quickly or flexibly: seasonal peaks (adding capacity for a few months of high demand without a multi-year fleet commitment), backup capacity during an AOG (aircraft-on-ground) event or unplanned maintenance, testing a new route or market before committing owned/dry-leased capacity to it, and pure cargo or charter operations where a specialist operator's crews and certifications are already in place.

It's also a real revenue opportunity for the SUPPLY side: airlines and dedicated ACMI operators (Atlas Air and Amerijet are well-known cargo-focused examples; passenger-side ACMI specialists and even mainline carriers themselves wet-lease out aircraft during their own off-peak periods) monetize aircraft and crew that would otherwise sit underutilized — a European charter carrier wet-leasing aircraft to a Gulf or Asian carrier during its own winter off-season is a commonly-seen pattern in the industry.

Regulatory and commercial considerations

Because the aircraft flies under the lessor's own certificate, safety oversight, crew licensing, and regulatory responsibility stay with the lessor — which is part of why customers value established ACMI operators with strong safety records and the right certifications for the markets involved. Cross-border wet leases can also involve additional regulatory approval (from both the lessor's and the operating market's aviation authorities) beyond what a domestic arrangement requires.

Risks and considerations

• Cost: ACMI capacity is generally priced at a premium to what the same block hours would cost on owned or dry-leased metal, since the customer is paying for flexibility and someone else's full operating infrastructure, not just the airframe.
• Brand and service-quality control: the flight may operate under the customer airline's own flight number and marketing (a common arrangement) even though crew, aircraft, and service standards are the ACMI provider's — a real coordination point for consistency.
• Availability is cyclical — ACMI capacity tends to be scarcest exactly when demand for it is highest (peak season, industry-wide AOG events tied to a specific engine or airframe issue), which can push rates up when an airline needs the flexibility most.