National Aeronautics and Space Administration chief Bill Nelson on Monday called billionaire Richard Branson’s historic flight with Virgin Galactic a “great” milestone for space exploration.

Branson, the founder of the Virgin Group, jetted into orbit on Sunday alongside two company employees and a pair of pilots as part of his company’s first full-crewed spaceflight, the Unity 22 Mission. The winged mothership, called the VMS Eve, took off from the Spaceport America runway in New Mexico and climbed nearly 300,000 feet above Earth at speeds slightly over Mach 3.