CAPE CANAVERAL, Fla. — Just over a day after blasting off, a SpaceX crew capsule arrived at the International Space Station on Sunday, delivering the replacements for NASA’s two stuck astronauts.

The four newcomers — representing the U.S., Japan and Russia — will spend the next few days learning the station’s ins and outs from Butch Wilmore and Suni Williams. Then the two will strap into their own SpaceX capsule later this week, one that has been up there since last year, to close out an unexpected extended mission that began last June.

Wilmore and Williams expected to be gone just a week when they launched on Boeing’s first astronaut flight. They hit the nine-month mark earlier this month.

The Boeing Starliner capsule encountered so many problems that NASA insisted it come back empty, leaving its test pilots behind to wait for a SpaceX lift.

Wilmore swung open the space station’s hatch and then rang the ship’s bell as the new arrivals floated in one by one and were greeted with hugs and handshakes. A video posted on X by NASA showed astronaut Nick Hague greeting the new arrivals wearing a grey alien mask.

“It was a wonderful day. Great to see our friends arrive,” Williams told Mission Control.

Wilmore’s and Williams’ ride arrived back in late September with a downsized crew of two and two empty seats reserved for the leg back. But more delays resulted when their replacements’ brand new capsule needed extensive battery repairs. An older capsule took its place, pushing up their return by a couple weeks to mid-March.

Weather permitting, the SpaceX capsule carrying Wilmore, Williams and two other astronauts will undock from the space station no earlier than Wednesday and splash down off Florida’s coast.

Until then, there will be 11 aboard the orbiting lab, representing the U.S., Russia and Japan.

The newest crew includes NASA’s Anne McClain and Nichole Ayers, both military pilots; and Japan’s Takuya Onishi and Russia’s Kirill Peskov, both former airline pilots.

They will spend the next six months at the space station, considered the normal stint, after springing Wilmore and Williams free.

“Spaceflight is tough, but humans are tougher,” McClain said minutes into the flight up to the space station.

Retired Navy captains who have lived at the space station before, Wilmore and Williams have repeatedly stressed that they support the decisions made by their NASA bosses since last summer. The two helped keep the station running — fixing a broken toilet, watering plants and conducting experiments — and even went out on a spacewalk together.

With nine spacewalks, Williams set a new record for women: the most time spent spacewalking over a career.

The SpaceX capsule is shown here docking to the International Space Station on Sunday. (NASA via AP)