On Tuesday, the administration announced that Boeing, headed by Dennis Muilenburg, and SpaceX, run by Elon Musk, had been awarded the additional missions—bringing each of their total number of NASA contracts to send people into space to six.

“Awarding these missions now will provide greater stability for the future space station crew rotation schedule, as well as reduce schedule and financial uncertainty for our providers,” Phil McAlister, director, NASA’s Commercial Spaceflight Development Division said in a statement. “The ability to turn on missions as needed to meet the needs of the space station program is an important aspect of the Commercial Crew Program.”

The Commercial Crew Program was created by NASA as a way to put astronauts into space using the private sector. But both Boeing and SpaceX will first have to pass their spacecrafts through NASA certification.

Boeing is scheduled to test an uncrewed version of its proposed flight, the CST-100 Starliner, in June 2018, followed by its crewed flight test in August 2018. SpaceX is expected to demonstrate an uncrewed version of its Crew Dragon flight to the space station in November 2017, followed by a crewed test in May 2018.