Two Nasa astronauts are due to head for the International Space Station aboard a new spacecraft.

Boeing’s Starliner will blast off from Cape Canaveral in Florida, in its first crewed test flight.

The mission has been delayed for several years because of setbacks in the spacecraft's development.

If it is successful, it will become the second private firm able to provide crew transport to and from the ISS, alongside Elon Musk's SpaceX.

Nasa no longer wants to own and operate such vehicles, preferring now to buy the service from the commercial sector.

The scheduled lift-off is set for 22:34 local time on Monday (03:34 BST Tuesday).

But the launch is also a moment of jeopardy for Boeing. Its airline business is under pressure because of a series of accidents. And the firm’s space sector is also under scrutiny following difficulties in developing Starliner itself.

“It’s a really big day for Boeing", commented Dr. Simeon Barber, a space scientist at the Open University.

“The company has been working on the spacecraft for so long, they have had a few problems with the test flights and there’s a lot riding on this”.

Starliner was originally due to have its first uncrewed test flight in 2015 but this was delayed until 2019. When it did occur, software glitches led to an internal clock malfunction, resulting in thrusters over-firing. So much fuel was consumed that the capsule couldn't reach the space station.

A second attempt was planned in August 2021 but delayed again until May 2022. An issue with the propulsion system was blamed. When Starliner did finally get off Earth, it managed to complete its full mission but concerns were then later raised about the performance of some thrusters and the craft's cooling system.