A Russian Soyuz spacecraft carrying two American astronauts and a Russian cosmonaut linked up with the international space station June 17, doubling the orbital outpost’s crew size.

The Soyuz TMA-19 docked with the space station at 6:21 p.m. EDT as both spacecraft passed 354 kilometers over the Atlantic Ocean near Argentina. The space station’s crew is back up to full strength, with six people now living at the orbiting lab.

Cosmonaut Fyodor Yurchikhin  commanded the Soyuz flight to the station, which began two days earlier with a predawn launch from the Baikonur Cosmodrome in Kazakhstan.

The Soyuz docking also marked a milestone for women in space. For the first time, there are two female astronauts — NASA astronauts Shannon Walker and Tracy Caldwell Dyson — serving together on a long-duration spaceflight.

Walker arrived on the new Soyuz, while Caldwell Dyson has been living on the space station with two Russian crewmates since early April. Their four male crewmates include three Russians and one American.

Yurchikhin and Walker arrived at the station with NASA astronaut Douglas Wheelock. The trio are beginning a five-and-a-half-month mission that, if all goes according to plan, should see the two final space shuttle missions before NASA retires its orbiter fleet later this year.

After that, NASA plans to rely on Russian Soyuz spacecraft to ferry astronauts to the space station until commercial American spacecraft become available.