Boeing’s troubled space capsule has finally made it off the launchpad with two astronauts on board.
The first crewed test flight of Starliner had been delayed by series of faults, either with the capsule or the rocket that fired it off pad 41 at Cape Canaveral in Florida.
Commander Butch Wilmore and colleague Suni Williams will dock with the International Space Station (ISS) on Thursday, where they will spend a week before returning to Earth.
Ms Williams is the first female test pilot of an orbital spacecraft.
NASA administrator Bill Nelson said: “Two bold NASA astronauts are well on their way on this historic first test flight of a brand-new spacecraft.”
“Boeing’s Starliner marks a new chapter of American exploration. Human spaceflight is a daring task – but that’s why it’s worth doing. It’s an exciting time for NASA, our commercial partners, and the future of exploration. Go Starliner, Go Butch and Suni!”
Three previous launch attempts this year were scrubbed, most recently on Saturday when mission control stopped the countdown with just three minutes and 50 seconds to go.
But Wednesday’s lift-off was textbook, with Starliner soaring into the blue sky on a United Launch Alliance rocket.
The capsule was launched on an unusual shallow ascent that gave the crew a better chance of aborting the flight if necessary all the way up to orbit. Other safety modifications were made to the rocket so the capsule could quickly separate in an emergency.
The capsule is a critical alternative to Space X’s Crew Dragon spacecraft and is currently the only shuttle for US, European, Canadian and Japanese astronauts to and from the ISS.
If NASA certifies Starliner after this test flight, Boeing is expected to begin operational flights in spring 2025.
NASA commissioned both Space X and Boeing to develop a commercial crew capsule in 2014.
But while Space X started shuttling astronauts in 2020, Boeing’s spacecraft has been mired in difficulties.
In its first uncrewed mission in 2019, a fault resulted in the capsule running out of fuel and docking with the ISS was aborted.
A second flight in 2022 was deemed a success by NASA, despite thruster problems, paving the way for a human test flight.
But planned launches last year were scrubbed because of overheating batteries, the discovery that protective tape around wiring was flammable and potentially catastrophic problems with the parachute system used for the capsule’s return to Earth.
Boeing’s losses on the Starliner programme are believed to be around $1.5bn (£1.2bn).
The company’s aircraft division has also been under intense scrutiny since a disused emergency exit door blew off one of its planes shortly after take-off in January.
The US air regulator, the Federal Aviation Administration, subsequently criticised the company’s quality control.