June 6 (Reuters) - Boeing's ( BA ) Starliner capsule

faces a crucial test on Thursday when it is expected to dock

with the International Space Station (ISS) on the spacecraft's

first trip to orbit carrying astronauts, as the aerospace giant

looks to sharpen its competition with Elon Musk's SpaceX.

The CST-100 Starliner, with astronauts Barry "Butch" Wilmore

and Sunita "Suni" Williams aboard, was launched from the Cape

Canaveral Space Force Station in Florida on Wednesday, strapped

to an Atlas V rocket furnished and flown by the Boeing-Lockheed

Martin joint venture United Launch Alliance (ULA).

The reusable gumdrop-shaped capsule and its crew have a

rendezvous with the ISS. It is scheduled at 12:15 p.m. ET (1615

GMT) to dock autonomously with the ISS, which orbits some 250

miles (400 km) above Earth. It is due to stay docked for about

eight days, then safely return the two astronauts to Earth,

among other flight objectives.

Its launch on Wednesday followed years of technical

problems, various delays and a successful 2022 test mission to

the orbital laboratory without astronauts aboard.

Boeing ( BA ) intends for Starliner - seeded with NASA funding - to

compete with SpaceX's Crew Dragon capsule, which since 2020 has

been the U.S. space agency's only vehicle for sending ISS crew

members to orbit from U.S. soil. The mission is a test flight

required before NASA can certify Starliner for routine astronaut

missions.

The seven-seat Starliner's inaugural crew includes two

veteran NASA astronauts in Wilmore, 61, a retired U.S. Navy

captain and fighter pilot, and Williams, 58, a former Navy

helicopter test pilot with experience flying more than 30

different aircraft.

Getting Starliner to this point has been a fraught process

for Boeing ( BA ) under its $4.2 billion fixed-priced contract with

NASA, which wants the redundancy of two different U.S. rides to

the ISS. The Starliner is several years behind schedule and more

than $1.5 billion over budget. Meanwhile, Boeing's ( BA ) commercial

airplane operations have been rocked by crises involving its 737

MAX jetliners.