LOS ANGELES -- The crew of the US Polaris Dawn mission returned to Earth early Sunday, completing the commercial human spaceflight mission.

SpaceX's Dragon spacecraft carrying four civilian astronauts splashed down off the coast of Dry Tortugas, Florida at 3:36 am Eastern Time Sunday (0736 GMT), according to SpaceX.

The four-member crew consists of mission commander Jared Isaacman, pilot Kidd Poteet, and specialists Sarah Gillis and Anna Menon.

The crew lifted off aboard the Dragon spacecraft on Tuesday from NASA's Kennedy Space Center in Florida. During their five-day space journey, they traveled as high as 1,400 km above Earth, the highest humans have traveled since the Apollo program over 50 years ago, according to SpaceX.

Two astronauts of the four-member crew, wearing SpaceX's newly-designed extravehicular activity suits, completed a spacewalk on Thursday, marking the first time astronauts have space-walked from a commercial spacecraft.

The crew conducted scientific experiments during their multi-day mission, including essential health and human performance research for NASA's Human Research Program. They also tested Starlink laser-based communications in space, according to the company.