Four astronauts, part of SpaceX and NASA's first commercial crew programme, returned to Earth safely on Sunday after their six-month mission aboard the International Space Station, the US space agency said.

The astronauts -- NASA's Michael Hopkins, Victor Glover, and Shannon Walker, along with Japan Aerospace Exploration Agency (JAXA) mission specialist Soichi Noguchi -- returned to Earth in a parachute-assisted splashdown at 2:56 a.m. EDT off the coast of Panama City, Florida on Sunday.