CAPE CANAVERAL, Florida, May 6 (Reuters) - Boeing's ( BA )

new Starliner astronaut capsule was poised for launch on

Monday night on a much-delayed first crewed test flight to

orbit, as the company scrambles to compete with Elon Musk's

SpaceX for a greater share of lucrative NASA business.

The CST-100 Starliner with two astronauts aboard was due for

liftoff at 10:34 p.m. (0234 GMT on Tuesday) from NASA's Kennedy

Space Center in Florida, carried atop an Atlas V rocket

furnished by the Boeing-Lockheed Martin joint venture

United Launch Alliance (ULA).

The gumdrop-shaped capsule and its crew are headed for a

rendezvous with the International Space Station (ISS), two years

after the Starliner completed its first test voyage to the

orbital laboratory without astronauts aboard.

Boeing ( BA ), whose commercial plane operations are in disarray

after several sequential crises, badly needs a space win for its

Starliner venture, a years-delayed program with more than $1

billion in cost overruns.

While Boeing ( BA ) has struggled, SpaceX has become a dependable

taxi to orbit for NASA, which is backing a new generation of

privately built spacecraft that can ferry its astronauts and

other customers to the ISS and, under the space agency's more

ambitious Artemis program, to the moon and eventually Mars.

Starliner would compete head-to-head with SpaceX's Crew

Dragon capsule, which since 2020 has been NASA's only vehicle

for sending ISS crew to orbit from U.S. soil.

Riding aboard the Starliner, designed to carry up to seven

crew members, are veteran NASA astronauts Barry "Butch" Wilmore,

61, a retired U.S. Navy captain, and Sunita "Sunni" Williams,

58, a former Navy aviator and test pilot.

They have logged a combined 500 days in space over the

course of two missions each to the space station. Wilmore is the

designated commander for Monday's flight, with Williams in the

pilot seat.

Although Starliner is designed to fly autonomously, the crew

can assume control of the spacecraft if necessary. The test

flight calls for Wilmore and Williams to practice maneuvering

the vehicle manually.

WEATHER FORECASTS FAVORABLE

Launch forecasts on Monday called for a 95% chance of

favorable weather conditions, and ULA said on social media that

"all systems remain 'go'" for an on-time liftoff.

The launch would mark the first crewed voyage to space using

an Atlas rocket since the storied family of Atlas launch

vehicles first sent astronauts, including John Glenn, on orbital

flights for NASA's Mercury program in the 1960s.

If all goes as planned, the capsule will arrive at the space

station after a flight of about 26 hours and dock with the

orbiting research outpost some 250 miles (400 km) above Earth

early on Wednesday.

Wilmore and Williams are expected to remain at the space

station for about a week before riding the Starliner back to

Earth for a parachute and airbag-assisted landing in the U.S.

Desert Southwest - a first for crewed NASA missions.

The test flight comes at an especially critical moment for

Boeing ( BA ). Its airplane business is dealing with fallout from a

midair blowout of a cabin panel door plug on a nearly new 737

MAX 9 in January, as well as previous deadly crashes of two 737

MAX jets.

Getting Starliner to this point has been a fraught process

for Boeing ( BA ), beset by years of development setbacks and more than

$1.5 billion in charges for the aerospace giant on a $4.2

billion fixed-priced contract with NASA.

The space agency wants the redundancy of having two

different U.S. rides to the ISS, which is expected to retire

around 2030. NASA is encouraging private development of new

space stations that could replace the ISS after its retirement,

potentially giving Starliner new destinations.

The first attempt by Boeing ( BA ) to send an uncrewed Starliner to

the space station in 2019 failed due to dozens of software and

engineering glitches. A second attempt in 2022 succeeded, paving

the way for Monday night's mission.

Depending on the outcome, Starliner is booked to fly at

least six more crewed missions to the space station for NASA.

At a pre-flight briefing with NASA officials on Friday,

Boeing ( BA ) vice president Mark Nappi said the company and the space

agency were "in total agreement" that the Starliner was ready to

fly with crew, adding, "we can't be more confident."

"Because it is a test flight, we give extra attention," NASA

chief Bill Nelson said. "That's why we put two test pilots on

board."