The flight was originally planned to take place on Wednesday, but this was later delayed to Saturday due to problematic weather conditions.

Nearly 24 hours after launching from Florida, the astronauts entered the ISS, marking the first US space capsule to do so with a crew since 2011.

The reason the spacecraft took so long to dock was that it had to make a number of manoeuvres to raise its orbit to the height of the ISS.

The Dragon Capsule docked autonomously with the space station and the astronauts had to wait for pressure and leak checks to be completed before exiting.

They were greeted by fellow American Chris Cassidy, as well as two other space station residents, Russia cosmonauts Anatoli Ivanishin and Ivan Vagner, as they made their way out of their spacecraft.

“I will tell you, the whole world saw this mission and we are so, so proud for everything you have done for our country and in fact to inspire the world,” Nasa administrator Jim Bridenstine said over a phone line from Mission Control.

“It’s great to get the United States back in the crewed launch business and we’re just really glad to be on board this magnificent complex,” Hurley said.

SpaceX has now become the first private company to send humans into space and it also marked the first time that commercially developed space vehicles were used by Nasa for such a feat.

Behnken said he and Hurley were able to get a few hours’ sleep during their 19-hour orbital journey, telling the administrator that “the first night is always a little bit of a challenge, but the Dragon is a slick vehicle and we had good airflow so we had an excellent evening.”

Their mission is expected to last up to four months, during which time they will take some “burden” off the currently residing astronauts to ensure the ISS operates at “peak possibility”.

Nasa last sent astronauts into space on a brand-new vehicle 40 years ago at the start of the space shuttle program.

Boeing has been working on its own launch system in competition with SpaceX after both firms received a combined $8bn in funding from Nasa. Its CST-100 Starliner vehicle expected to ferry astronauts into space for the first time next year.