In a wet lease arrangement, the financing entity, or lessor, provides the aircraft, and complete crew, maintenance and insurance (ACMI) to another party at a cost based on hours of operation over a set time period. The lessee pays for fuel, airport fees, duties, taxes and other operational costs. Wet leases generally are established for one to 24 months. (Any shorter period would be considered simply ad hoc charter, which can be thought of as wet lease by the hour or mission.) In the commercial airline world, wet leases are typically utilized to provide supplemental lift during peak traffic seasons or during annual heavy maintenance checks. In the United Kingdom, a wet lease is employed whenever an aircraft is operated under the air operator's certificate (AOC) of the lessor.
The forward wing sweep, 20,280 pounds (9.20 t) MOTW Hamburger Flugzeugbau HFB 320 Hansa Jet first flew on 21 April 1964, powered by two General Electric CJ610, 47 were built between 1965 and 1973. The joint Piaggo-Douglas, 18,000 pounds (8.2 t) MOTW Piaggio PD.808 first flew on 29 August 1964, powered by two Armstrong Siddeley Vipers, 24 were built for the Italian Air Force.