Boeing's Starliner 'working toward' early June launch for Crew Flight Test

May 23 (UPI) -- After multiple delays, NASA, Boeing and United Launch Alliance said they are working toward a launch of the Boeing Starliner astronaut mission to the International Space Station as early as June 1.

NASA said Thursday that mission teams are working toward a launch opportunity at 12:25 p.m. EDT June 1, with additional opportunities June 2, 5 and 6.

"There has been a great deal of exceptional analysis and testing over the last two weeks by the joint NASA, Boeing, and ULA teams to replace the Centaur Self Regulating Valve and troubleshoot the Starliner Service Module helium manifold leak," Steve Stich, manager of the NASA Commercial Crew Program, said in a statement,

Stich added it's been important to understand all the complexities of each issue, as astronauts Butch Wilmore and Suni Williams will be aboard Starliner's Crew Flight Test mission.

"We will launch Butch and Suni on this test mission after the entire community has reviewed the teams' progress and flight rationale at the upcoming Delta Agency Flight Test Readiness Review," he said.

Mission managers said work continues to assess Starliner's performance and redundancy following the latest problem that delayed the launch -- a helium leak in the spacecraft's service module.

The mission team said they are completing "a follow-on propulsion system assessment to understand potential helium system impacts on some Starliner return scenarios."

There will also be a Flight Test Readiness Review, but the date of that review hasn't yet been determined.

NASA said the astronauts are still in quarantine and are practicing in Starliner simulators to prepare for their flight.

After an original May 6 launch date was scrubbed, Starliner's launch was postponed multiple times due to several issues.