The launches will mark the first manned flights to take off from U.S. soil since the space shuttle program was retired in 2011. Since then, NASA’s astronauts have reached the ISS on Russian Soyuz rockets launched from Kazakhstan, for which the U.S. had to pay tens of millions of dollars per seat.

The planned rocket launches will mark a major milestone for NASA. SpaceX’s and Boeing’s rockets will be the first commercially-developed vehicles to transport astronauts to the ISS.

The SpaceX rocket will be crewed by Dr. Bob Behnken, a Space Shuttle Endeavour veteran with more than 37 hours of spacewalk experience, and Doug Hurley, who piloted the Endeavour on its July 2009 mission.

Boeing’s Starliner mission will include Chris Ferguson, a Boeing astronaut who, while previously working for NASA, served as commander of two NASA flights. He will be joined by Eric Boe, who has experience on both the Endeavour and Space Shuttle Discovery (which he piloted in its final mission in February 2011), and Nicole Aunapu Mann, an experienced test pilot and lieutenant colonel in the Marines. This will be Mann’s first trip into space.

The Starliner mission was originally planned to last two weeks, but it may be extended into a six-month stay at the International Space Station (ISS), NASA says.

SpaceX’s first flight test is scheduled for April 2019, while Boeing’s is planned for mid-2019. But NASA warns that these dates are just targets, and both commercial providers have “more work ahead of them” before they can launch to the ISS.

Those tests, which involve brief stays at the ISS, will be followed by two others that will deliver the astronauts to extended stays at the orbiting station.

The Dragon’s first so-called operational mission will be manned by Victor Glover, a Navy commander, Naval aviator, and test pilot who will be making his first space flight. He will be joined by Mike Hopkins, a veteran astronaut with more than 160 days at the ISS. Both Glover and Hopkins will remain on the ISS for an extended stay.

The Starliner’s long-duration operational mission will be crewed by John Cassada, a Navy commander and experienced test pilot. On his first flight into space, Cassada will be joined by veteran astronaut Sunita Williams, who has spent 322 days in space, served as commander of the ISS, and performed seven spacewalks.

These missions are a part of NASA’s initiative to use commercial aircraft in its space exploration. According to The Washington Post, Boeing and SpaceX were awarded a total of $6.8 billion in 2014 to create spacecraft for transporting crews to the International Space Station.