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SpaceX will bring its Crew Dragon spacecraft home from the International Space Station Friday, capping its historic first test flight.

If all goes well, it’ll bring SpaceX one step closer to ending the United States’ years-long reliance on Russia to fly NASA astronauts to and from the ISS. Crew Dragon is SpaceX’s first capsule built to carry humans.

At about 2:30 am ET on Friday, Crew Dragon will unlatch from the ISS and continue to zip through orbit for the next five hours. It’ll then spend about 15 minutes firing its engines to slow its descent, allowing the spacecraft to safely cut back through the Earth’s thick atmosphere.

Finally, Crew Dragon, will deploy a plume of parachutes and drift to a landing in the Atlantic Ocean where recovery ships will be standing by to haul it out of the water.

The trip back to Earth will be a final key test for Crew Dragon, which launched an uncrewed demonstration mission on Saturday and linked up with the ISS on Sunday.

SpaceX's Crew Dragon docking with the International Space Station.

NASA has been unable to fly humans since the final Space Shuttle retired in 2011. NASA turned to the private sector to develop the next generation of human spaceflight hardware.

SpaceX and Boeing (BA), which is building a vehicle called Starliner, have contracts worth up to $2.6 billion and $4.2 billion, respectively. NASA hoped their spacecrafts would start flying in 2017. Both SpaceX and Boeing (BA) have been hampered with delays — but 2019 could be the year they start flying crew.

NASA is still concerned about safety with both spacecrafts, according to a recent Reuters report and documents from NASA’s safety advisory panel. Those issues still need to be resolved before NASA will fly its astronauts in SpaceX or Boeing’s spacecrafts.

But Elon Musk’s space exploration company is one step ahead of Boeing, as it will get key data from this demo mission to make final adjustments ahead of its inaugural crewed flight.

Crew Dragon also aced a key NASA review ahead of launch, and the space agency hasn’t reported any issues with the mission thus far.

The spacecraft will need to make a safe descent on Friday. The landing technique will be unique to SpaceX, as both Russia’s veteran Soyuz capsule and Boeing’s forthcoming Starliner are designed to land on terra firma rather than at sea.

A final key test on Crew Dragon’s emergency abort system is scheduled for June. And the first crewed mission, which will carry astronauts Doug Hurley and Bob Behnken, is slated for July, according to NASA’s most recent schedule.

The timeline for Boeing’s Starliner is not as clear. It’s slated to fly its first uncrewed demo mission no earlier than April.