After a brief hangup caused by wayward fumes given off by propellant, the Crew Dragon opened its hatch and Behnken and Hurley took their first steps into Earth's gravity after spending two months in the zero-G environment of space.

Behnken waved to the cameras before heading to his medical check up. Hurley followed shortly after and flashed a thumb's up.

The astronauts are now on board SpaceX's GO Navigator recovery vessel and will soon take a helicopter flight back to terra firma.

"Thanks for doing the most difficult part and the most important part," Hurley said to mission control shortly before departing.

Spending two months in microgravity, then enduring a jarring trip home, can make readjusting difficult.

NASA astronaut Garret Reisman, who helped SpaceX develop Crew Dragon, said it took him about 15 minutes to sit up and another 15 to be able to stand after he returned to Earth after Space Shuttle missions.