What is a wet lease?
A wet lease is an arrangement where one airline supplies another with an aircraft, complete crew, maintenance and insurance. The flight is sold under the hiring airline's code, but the aircraft, cabin and crew belong to the operator, which is why the experience can differ from expectation.
Wet lease explained
The industry shorthand is ACMI, for aircraft, crew, maintenance and insurance. A dry lease by contrast supplies the aircraft alone, and the hiring airline puts its own crew and maintenance behind it. Between them sit damp leases, which usually mean flight crew from the operator and cabin crew from the customer.
Airlines reach for wet leases when demand outruns their own fleet or when something goes wrong. Seasonal peaks, a delayed aircraft delivery and unexpected grounding all produce short term holes that a leased aircraft fills faster than any other option. Some carriers also use them to test a new route before committing their own metal to it.
For passengers the consequence is the cabin. A wet leased aircraft carries the operator's seats, its catering standard and its crew, not the brand you booked. On a premium ticket that can mean a recliner where the airline's own fleet would have offered a flat bed, and it is the single most common cause of an unexpected downgrade in product.
It is usually visible before departure if you look. The booking will name an operating carrier different from the marketing airline, and the aircraft type sometimes changes from the one originally scheduled. Checking the operating carrier rather than the code on the ticket is the reliable way to know what cabin you are actually buying.
More on wet lease
A wet lease supplies the aircraft with crew, maintenance and insurance included. A dry lease supplies the aircraft alone, and the hiring airline operates it with its own crew under its own certificate.
To cover demand their own fleet cannot meet, to replace an aircraft that is delayed or grounded, and sometimes to trial a new route before committing their own aircraft to it.
It can, and this is the part that matters most. The aircraft carries the operator's seats and catering, not the marketing airline's. On premium tickets that occasionally means a different seat type than the fleet you expected.
The booking names an operating carrier different from the airline you bought from. Checking that field, rather than the flight code, tells you whose aircraft and cabin you will actually be flying in.
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