US: NASA’s two stuck astronauts may end up back on Earth a little sooner than planned. The space agency announced Tuesday that SpaceX will switch capsules for upcoming astronaut flights in order to bring Butch Wilmore and Suni Williams home in mid-March instead of late March or April. That will shave at least a couple weeks off their prolonged stay at the International Space Station, which hit the eight-month mark last week. “Human spaceflight is full of unexpected challenges,” NASA’s commercial crew program manager Steve Stich said in a statement.

The test pilots should have returned in June on Boeing’s Starliner capsule after what should have been a weeklong flight demo. But the capsule had so much trouble getting to the space station that NASA decided to bring it back empty and reassigned the pair to SpaceX.

Then SpaceX delayed the launch of their replacements on a brand new capsule that needed more prepping, which added more time to Wilmore and Williams’ mission. With even more work still anticipated for the new capsule, NASA opted for its next crew to fly up on an older capsule, with liftoff now targeted for March 12. This older capsule had already been assigned to a private crew awaiting launch this spring.

The private flight arranged by the Houston company Axiom Space, featuring astronauts from Poland, Hungary and India, was bumped and will launch later to the space station, possibly still this spring. NASA prefers having a new crew arrive before sending the old one back, in this case Wilmore, Williams and two others up there since September. The new crew going up includes two NASA astronauts, as well as one from Japan and one from Russia.

NASA’s latest change in plans comes two weeks after the space agency said it was working “expeditiously” to bring back Wilmore and Williams as soon as possible. Just a day earlier, President Donald Trump and SpaceX’s Elon Musk had vowed to accelerate the astronauts’ return.