WASHINGTON • America's first crewed spaceship to fly to the International Space Station (ISS) in nearly a decade returned safely to Earth on Sunday, splashing down in the Gulf of Mexico.

The mission, carried out jointly by Nasa (National Aeronautics and Space Administration) and SpaceX, shows that the US has the capacity once more to send its astronauts to space and bring them back.

The SpaceX Crew Dragon Endeavour splashed into the waters off Pensacola, Florida at 2.48pm (2.48am Monday Singapore time), trailed by its four main parachutes.

It was the first water landing for a crewed US spaceship since the 1975 Apollo-Soyuz mission.

"It's truly our honour and privilege," said pilot Doug Hurley, who was joined on the mission by commander Bob Behnken.

"On behalf of Nasa and SpaceX teams, welcome back to planet Earth and thanks for flying SpaceX," replied SpaceX senior engineer Mike Heiman, to laughter in the control room.

A flotilla of civilian boats swarmed the landing zone as a recovery ship sped to the scorched capsule and hoisted it aboard with its crane.

The coast guard said it had warned people to stay away from the capsule, but "numerous boaters" ignored the requests.

The opening of the hatch was delayed as a team worked to stop a potentially dangerous leak of rocket fuel vapour.

Nasa administrator Jim Bridenstine said: "What's not common is having passers-by approach the vehicle at close range with nitrogen-tetroxide in the atmosphere... We need to make sure we're warning people not to get close to the spacecraft in the future."

About an hour after splashdown, the astronauts left the capsule and headed for shore in a helicopter.

A visibly excited SpaceX founder Elon Musk said that the mission heralded a new era.

"We're going to go to the Moon, we're going to have a base on the Moon; we're going to Mars," he said. "I'm not very religious but I prayed for this one."

US President Donald Trump - who had travelled to Florida for the capsule's launch two months ago - hailed its safe return.

The United States has had to rely on Russia for rides to space since the country's last Space Shuttle flew in 2011.

The mission is also a huge win for SpaceX, which was founded in 2002 but has leapfrogged its way past Boeing, its main competitor in the commercial space race.

The US paid the two companies a total of about US$7 billion (S$9.6 billion) for their "space taxi" contracts, though aerospace giant Boeing's efforts have floundered.

The Crew Dragon capsule performed several precisely choreographed sequences to return home safely.

First, it jettisoned its "trunk" that contains its power, heat and other systems, which burned up in the atmosphere.

It then fired its thrusters to manoeuvre into the proper orbit and trajectory for splashdown. As it re-entered the atmosphere at a speed of around 28,000kmh, it experienced temperatures of 1,900 deg C.

It used two sets of parachutes on its descent, bringing its speed down as it hit the Gulf of Mexico.

Endeavour will now undergo a six-week inspection to certify the vessel as worthy of future low-Earth orbit missions.

The next mission, dubbed "Crew-1", will involve a team of four: three Nasa astronauts and Japan Aerospace Exploration Agency mission specialist Soichi Noguchi.

The launch is set for late next month, and the crew is due to spend six months at the space station.

AGENCE FRANCE-PRESSE