SpaceX has received a second contract from Nasa to take astronauts to the International space Station.
The award is seen as another important step in returning U.S. astronaut launches from U.S. soil.
Currently, Russian Soyuz craft are Nasa's only option since the end of the Space Shuttle programme.
It is the fourth and final guaranteed order NASA will make under the Commercial Crew Transportation Capability (CCtCap) contracts.
Boeing received its two orders in May and December of 2015, and SpaceX received its first order in November 2015.
Both companies have started planning for, building and testing the necessary hardware and assets to carry out their first flight tests, and ultimately missions for the agency.
At a later time, NASA will identify which company will fly the first post-certification mission to the space station. Each provider's contract includes a minimum of two and a maximum potential of six missions.
SpaceX is building four Crew Dragon spacecraft at its Hawthorne facility -- two for qualification testing and two for flight tests next year.
The company also is in the process of modifying Launch Pad 39A at NASA's Kennedy Space Center in Florida, from which the company will launch future crewed missions to the space station.
A standard commercial crew mission to the station will carry as many as four crew members and about 220 pounds of pressurized cargo, and remain at the station for as long as 210 days, available as an emergency lifeboat during that time.
The fourth Falcon 9 rocket carried the Thaicom 8 communications satellite into orbit in May this year before landing safely, marking the company's fourth successfully landing.
Now the company has begun testing this rocket as it prepares to meet its goal of relaunching a 'reusable' rocket by October.