The US Federal Aviation Administration defines a large aircraft as any aircraft with a certified maximum takeoff weight (MTOW) of more than 12,500 lb (5,700 kg) [1]

The European Aviation Safety Agency (EASA) defines a large aircraft as either "an aircraft with a maximum take-off mass of more than 5,700 kilograms (12,600 pounds) or a multi-engined helicopter."

It was originally developed during the 1980s as an enlarged derivative of the Antonov An-124 airlifter for the express purpose of transporting Buran orbiters. On 21 December 1988, the An-225 performed its maiden flight; Only one aircraft was ever completed, although a second airframe with a slightly different configuration was partially built. After a brief period of use supporting the Soviet space program, the aircraft was mothballed during the early 1990s. Towards the turn of the century, it was decided to refurbish the An-225 and reintroduce it for commercial operations, carrying oversized payloads for the operator Antonov Airlines. Multiple announcements were made regarding the potential completion of the second airframe, though its construction largely remained on hold due to a lack of funding. By 2009, it had reportedly been brought up to 60–70% completion.