NASA has scrubbed its launch to take four astronauts to the International Space Station, which is one of the first steps in returning NASA astronauts Suni Williams and Butch Wilmore’s back to Earth. NBC News' Tom Costello has more on the reasons for the scrub.

The crew-swap mission will enable NASA’s Butch Wilmore and Suni Williams to return home from the International Space Station.

Reaching orbit from NASA’s Kennedy Space Center, 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.