[2][3][needs update] It was also the first ship of the Scaled Composites Model 339 SpaceShipTwo class, based on upscaling the design of record-breaking SpaceShipOne.

[6] Enterprise was destroyed during a powered test flight on 31 October 2014, killing one pilot, Michael Alsbury, and seriously injuring another, Peter Siebold.

[8][9][10] Initial projections by Virgin Galactic in 2008 called for test flights to begin in late 2009 and commercial service to start in 2011.

The craft remained attached to VMS Eve as planned, and underwent a series of combined vehicle systems tests.

A second, similar crewed flight of VSS Enterprise and VMS Eve was carried out on 30 September 2010, lasting approximately 5 hours.

[28][30] In September 2012, Virgin Galactic announced that the unpowered subsonic glide flight test program was essentially complete.

It broke the sound barrier, reached Mach 1.43, and climbed to 69,000 feet (21 km) over the Mojave Desert under rocket power and descended using its tilt-wing "feathering" maneuver.

[53] The pilot in command, Peter Siebold, escaped from the craft and parachuted to safety; the copilot, Michael Alsbury, was killed in the crash.

In July 2015, the NTSB released a report that cited inadequate design safeguards, poor pilot training, lack of rigorous federal oversight and a potentially anxious co-pilot without recent flight experience as important factors in the crash.

[10] The NTSB determined that the crash resulted from the co-pilot's premature deployment of the feathering mechanism, which is normally used to aid a safe descent.

The NTSB also faulted the ship's designers for failing to protect against human error, noting that the spacecraft lacked fail-safe systems that would have prevented or deterred a premature deployment of the feathering mechanism.