NASA has ordered a second mission from Boeing to take astronauts to the International Space Station.

It’s all part of an ongoing effort by the space agency to establish regular crew missions that will launch from the United States.

An image of the International Space Station over Earth. (NASA)

Boeing is one of two private companies building vehicles to transport astronauts to the ISS through NASA’s Commercial Crew Program; SpaceX is the other.

The contracts given to these companies are designed to reduce the cost of sending American astronauts to the ISS—the U.S. currently relies on hitching a ride aboard the Russian Soyuz rocket.

“Placing orders for those missions now really sets us up for a sustainable future aboard the International Space Station, said Kathy Lueders, manager of NASA’s Commercial Crew Program.

NASA ordered its first crewed mission from Boeing in May. SpaceX received the second order in November. No word yet which company will be the first to launch NASA astronauts.

Crewed flights from American soil aren’t expected to begin until 2017.