Boeing and Pretoria-born Elon Musk's Space Exploration Technologies Corporation will share a multibillion-dollar contract to help restart US manned space flights.
The funding is for the right to build the first US-manned craft since Nasa retired the space shuttle fleet in 2011.
Nasa now uses Russian rockets to get people to the International Space Station. Boeing and SpaceX competed with Sierra Nevada Corp.
Nasa is charting a new direction 45 years after sending humans to the moon, looking to private industry to take over human missions near Earth with reusable craft.
Commercial operators will develop space tourism while the agency focuses on far-off missions to Mars.
Spending on the programme may reach $3.42-billion by 2020.