A SpaceX Crew Dragon capsule carrying four astronauts splashed down in the Gulf of Mexico in the early hours of Sunday morning, in Nasa’s first night-time ocean landing since the Apollo 8 Moon mission in 1968.
The crew reported feeling well after arriving back on Earth at the end of an almost six-month stay aboard the International Space Station, Nasa said.
Night vision imagery captured by one of Nasa’s experimental high-altitude research planes showed the capsule descending under its parachutes, landing safely off the coast of Panama City after a six-and-a-half-hour flight from the ISS.
“We welcome you back to planet Earth and thanks for flying SpaceX,” SpaceX’s Mission Control radioed moments after splashdown.
“For those of you enrolled in our frequent flyer programme, you’ve earned 68 million miles on this voyage.”
“We’ll take those miles,” said spacecraft commander Mike Hopkins. “Are they transferrable?”
SpaceX replied that the astronauts would have to check with the company’s marketing department.
Within a few minutes, Mr Hopkins reported he could see light from the approaching recovery boats out the capsule’s window.
He was the first to emerge after the hatch was opened, dancing as he set foot on deck.
"On behalf of Crew-1 and our families, we just want to say thank you ... It's amazing what can be accomplished when people come together. Y'all are changing the world. Congratulations. It's great to be back," Mr Hopkins said in a Nasa tweet.
Fellow Nasa astronauts Victor Glover, Shannon Walker and Japan's Soichi Noguchi were the other three aboard.
"Welcome home Victor, Michael, Shannon, and Soichi, and congratulations to the teams at Nasa and SpaceX who worked so hard to ensure their safe and successful splashdown," said new Nasa administrator Bill Nelson.
"We've accomplished another incredible spaceflight for America and our commercial and international partners. Safe, reliable transportation to the International Space Station is exactly the vision that Nasa had when the agency embarked on the commercial crew programme."
The four astronauts flew to space last November as the crew on the first fully operational mission to the ISS aboard a vehicle made by Elon Musk's SpaceX, which has become Nasa's favoured commercial transportation partner.
The 167-day mission is the longest for astronauts launching from the US. The previous record of 84 days was set by Nasa’s final Skylab station crew in 1974.
After medical checks, the four astronauts were due to be flown by helicopter to Pensacola to board a plane for Houston to be reunited with their friends and family, Nasa said.
"The reports are all four crew members are in great shape and in great spirits and doing really well," Nasa chief flight director Holly Ridings said at a post-landing news briefing.
"Really just a great day. It's not very often you get to wake up on the Space Station and go to sleep in Houston," she said.
Hiroshi Sasaki, vice president of human spaceflight technology at Japan’s space agency, Jaxa, told Nasa television that the mission “opened a new era for human space flight”.
The replacements for the four returning astronauts – from the US, Japan and France – arrived at the space station last weekend in their own SpaceX capsule for a six-month mission.
The three other crew currently aboard the ISS – one American and two Russians – arrived in a Russian capsule launched from Kazakhstan three weeks ago.
As the SpaceX capsule detached from the space station, Mr Hopkins thanked the crew left behind for their hospitality.
"We'll see you back on Earth," he said.
SpaceX made history last year when two American astronauts, Bob Behnken and Doug Hurley, carried out a test flight to the ISS in May and stayed for two months.
It was the first launch to the ISS from US soil since the end of the Space Shuttle programme in 2011, and the first crewed mission run by a private company.
Until then, US astronauts had flown to the ISS on board Russian Soyuz rockets.
SpaceX plans to use a modified version of its Crew Dragon capsule fitted with an observation dome to send an all-civilian crew into space for the first time this year.
All four crew members of the Inspiration4 mission have now been selected for the pioneering flight, with SpaceX targeting a launch date of no earlier than September 15.
Speaking to Nasa television, SpaceX flight reliability adviser Hans Koenigsmann said: “We’re ready for the private astronaut mission.”