Space launch company Stratolaunch has successfully completed the long-anticipated first flight of its 385-ft.-span, six-engine mothership at Mojave Air & Spaceport. The first flight, which began at 6.58 a.m. Pacific and ended at 9.26 a.m. on Mojave’s 200-ft.-wide runway 30, saw the aircraft put through basic handling qualities tests at speeds up to 164 kt. (189 mph) and altitudes up to 15,000 ft.

The flight marks a key milestone for Stratolaunch, which late company founder Paul Allen unveiled together with Rutan in late 2011. Development of the huge aircraft, however, has taken far longer than anticipated and the initial flight comes almost two years after it was first rolled out and 16 months after initial taxi tests.