“That was one heck of a ride,” the commander of four astronauts on a SpaceX rocket ship radioed back to Earth as they began their historic flight to the International Space Station on Monday.

The mission, which thundered into the night from the Kennedy Space Centre in Cape Canaveral, Florida, at 11.27am Australian time on Monday, is the first time NASA has sent a crew into orbit aboard a privately owned spacecraft.

“By working together through these difficult times, you’ve inspired the nation, the world, and in no small part the name of this incredible vehicle, Resilience,” Commander Mike Hopkins said right before liftoff.

The four crew will spend 27 hours inside SpaceX’s Crew Drago capsule, dubbed Resilience, before reaching the International Space Station, where they will spend the next six months.

Tweet from @NASA

An air leak caused an unexpected drop in capsule pressure less than two hours before launch but technicians said they conducted a successful check and the scheduled launch was still on.

The crew were supposed to head to the orbiting laboratory 400 kilometres above Earth on Saturday.

However, the launch was postponed for a day due to forecasts of gusty winds – remnants of Tropical Storm Eta – that would have made a return landing for the Falcon 9’s reusable booster stage difficult, NASA said.

The astronauts donned their custom white flight suits and arrived at the Kennedy Space Centre launch pad on schedule at 4.30pm in three white Tesla SUVs, flanked by NASA and SpaceX personnel.

Vice-President Mike Pence attended the launch and said beforehand that under President Donald Trump, America had “renewed our commitment to lead in human space exploration”.

President-elect Joe Biden Tweeted his congratulations, saying the launch was “a testament to the power of science”.

Tweet from @NASA

NASA called the flight its first “operational” mission for a rocket and crew-vehicle system that was 10 years in the making.

It represents a new era of commercially developed spacecraft – owned and operated by a private entity rather than NASA – for sending Americans into orbit.

A trial flight of the SpaceX Crew Dragon in August, carrying just two astronauts to and from the space station, marked NASA’s first human space mission to be launched from US soil in nine years, following the end of the space shuttle program in 2011.

In the intervening years, US astronauts have had to hitch rides into orbit aboard Russia’s Soyuz spacecraft.

The crew of Victor Glover, Michael Hopkins, Shannon Walker and Soichi Noguchi head for the launch zone. Photo: Getty

The Resilience crew includes commander Hopkins and fellow NASA astronauts, mission pilot Victor Glover and physicist Shannon Walker.

They were joined by Japanese astronaut Soichi Noguchi, making his third trip to space after previously flying on the US shuttle in 2005 and Soyuz in 2009.

Elon Musk, the billionaire SpaceX chief executive who is also CEO of electric carmaker and battery manufacturer Tesla, did not watch the liftoff from the Kennedy Space Centre launch control room as usual, NASA officials said.

On Saturday, Mr Musk said he “most likely” has a moderate case of COVID-19.

-with agencies