The first test flights are planned to begin in 2017, with a goal of a commercial launch by 2020. The first flight of the carrier aircraft had been pushed back until 2018 at the earliest, with the first flight of the air-launched rocket expected at the earliest 2019.
Paul Allen and Burt Rutan stated that Stratolaunch's carrier aircraft would have a wingspan of 117 m (385 ft) or about 6.1 m (20 ft) longer than an Apollo-era Saturn V and about half as long as the Hindenburg class airships. This would make it the largest airplane, by wingspan, ever to fly. It will weigh in at over 540,000 kg (1,200,000 lb) including the fully fueled launch vehicle and will require a runway at least 3,700 m (12,000 ft) long. It can carry over 230,000 kg (500,000 lb) of payload.
The Antonov An-225 Mriya is the current plane with the largest payload capacity. The An-224 airlifter holds the absolute world records for an airlifted single-item payload of 189,980 kilograms (418,830 pounds), and an airlifted total payload of 253,820 kg (559,580 lb). It has also transported a payload of 247,000 kg (545,000 lb) on a commercial flight. On 30 August 2016, Antonov agreed to complete the second airframe for Aerospace Industry Corporation of China.
They were originally going to launch Falcon 9 Air with a payload of 6100 kg. However, Spacex dropped out of the partnership.