SpaceShipOne was developed by Mojave Aerospace Ventures without government funding. On June 21, 2004, it made the first privately funded human spaceflight.  During its test programme, SpaceShipOne set a number of important "firsts", including first privately funded aircraft to exceed Mach 2 and Mach 3, first privately funded manned spacecraft to exceed 100km altitude, and first privately funded reusable manned spacecraft.

SpaceShipOne is an experimental air-launched rocket-powered aircraft with suborbital flight capability that uses a hybrid rocket motor. The design features a unique "feathering" atmospheric reentry system where the rear half of the wing and the twin tail booms folded upward along a hinge running the length of the wing; this increased drag while remaining stable. The achievements of SpaceShipOne are more comparable to the X-15 than orbiting spacecraft like the Space Shuttle. Accelerating a spacecraft to orbital speed requires more than 60 times as much energy as accelerating it to Mach 3.