Keeping tabs on uncertain weather, mission managers decided Saturday to press ahead with an attempt to launch three astronauts and a Russian cosmonaut on a flight to the International Space Station.

Crew 8 commander Matthew Dominick, co-pilot Michael Barratt, Jeanette Epps and cosmonaut Alexander Grebenkin planned to strap into their Crew Dragon spacecraft around 9 p.m. EST to await launch from pad 39A at the Kennedy Space Center at 11:16 p.m. EST.

If all goes well, the rocket’s reusable first stage, making its maiden flight, will fly itself back to landing at the nearby Cape Canaveral Space Force Station after boosting the upper stage and Crew Dragon out of the lower atmosphere. The Crew Dragon is expected to be released to fly on its own 12 minutes after liftoff.

NASA and SpaceX originally targeted launch for early Friday, but high winds and rough seas in the Atlantic Ocean, where the crew might have to splash down in an abort, prompted a two-day delay. Offshore conditions were still marginal Saturday, sources said, but mission managers opted to press ahead with the countdown.

Assuming an on-time launch, the Crew Dragon “Endeavour” is expected to catch up with the space station Sunday, moving in from behind and below. After looping up to a point directly in front of the outpost, Endeavour will press in for an autonomous docking at the lab’s forward port at 2:15 p.m.

Standing by to welcome Crew 8 aboard will be Soyuz crewmates Oleg Kononenko, Nikolai Chub and NASA astronaut Loral O’Hara, who were launched to the station last September.

Also on board: Crew 7 commander Jasmin Moghbeli, European Space Agency astronaut Andreas Mogensen, Japanese flier Satoshi Furukawa and cosmonaut Konstantin Borisov, launched from the Kennedy Space Center last August. Winding up a 198-day mission, they’re being replaced by Crew 8.

After Moghbeli and her crewmates depart on March 10, the Russian federal space agency Roscosmos plans to launch veteran cosmonaut Oleg Novitskiy, Belarus guest flier Marina Vasilevskaya and NASA veteran Tracy Dyson on March 21 aboard the Soyuz MS-25/71S ferry ship.

The goal of the mission is to ferry Dyson to the station for a six-month stay and to deliver a fresh Soyuz for Kononenko and Chub, who are midway through a yearlong stay in space.

Novitskiy and Vasilevskaya will return to Earth April 2, along with NASA’s O’Hara, using the Soyuz MS-24/70S spacecraft that carried Kononenko, Chub and O’Hara to the station last September.

Dyson will return to Earth in September, joining Kononenko and Chub aboard the Soyuz MS-25/71S spacecraft delivered by Novitskiy. Including four earlier flights, Kononenko will have logged more than 1,100 days in orbit overall, setting a new world record for most time in space.