Boeing‘s Starliner undocked from the International Space Station on Friday, months later than the spacecraft was originally supposed to depart — and without the two astronauts that it delivered to orbit in early June.

Instead, NASA test pilots Butch Wilmore and Suni Williams will stay at the ISS for the rest of the year and will return to Earth in February aboard SpaceX’s Dragon spacecraft.

It left the space station at 6:04 p.m. ET Friday. The capsule is expected to take about six hours to return to Earth and reach a landing zone at White Sands Space Harbor in New Mexico. NASA said it could be visible from parts of western Mexico and the Southwestern United States before landing.

The undocking process will work slightly different than it would have with a crew, in an effort to protect the ISS and because astronauts will not be on board to take manual control if necessary, NASA officials said Wednesday.

“We have your backs, and you’ve got this,” Williams told mission controllers at NASA’s Johnson Space Center in Houston on Friday before the undocking. “Bring her back to Earth. Good luck.”

The return of Boeing’s Starliner capsule “Calypso” ends a test flight that was ultimately much longer than NASA initially predicted — and that did not go as planned. The agency delayed the spacecraft’s return multiple times, citing the desire to gather more data about its problematic propulsion system.

Starliner, initially expected to be in space for about nine days, spent roughly three months at the ISS while Boeing investigated an issue with the capsule’s thrusters. Boeing officials were adamant in press briefings that Starliner was safe for the astronauts to fly home in the event of an emergency, even though they delayed the return multiple times.

But NASA officials ultimately decided in late August that the agency would send Starliner back empty, saying it wants to “further understand the root causes” of the spacecraft’s issues.

The Starliner crew flight test was supposed to be a final step for Boeing and a key addition for NASA. The agency was hoping to have two competing companies — Boeing and Elon Musk‘s SpaceX — with the ability to fly alternating missions to the ISS.

Instead, the test flight has set Boeing’s progress in NASA’s Commercial Crew Program back and, with more than $1.5 billion in losses absorbed already, could threaten the company’s future involvement with it.