Enlarge / Boeing's Starliner spacecraft sits on top of a United Launch Alliance Atlas V rocket at Cape Canaveral Space Force Station, Florida. (credit: NASA/Joel Kowsky)

NASA and Boeing officials are ready for a second attempt to launch the first crew test flight on the Starliner spacecraft Saturday from Cape Canaveral Space Force Station, Florida.

Liftoff of Boeing's Starliner capsuled atop a United Launch Alliance Atlas V rocket is set for 12:25 pm EDT (16:25 UTC). NASA commander Butch Wilmore and pilot Suni Williams, both veteran astronauts, will take the Starliner spacecraft on its first trip into low-Earth orbit with a crew on board.

You can watch NASA TV's live coverage of the countdown and launch below.

Enlarge / Boeing's Starliner spacecraft atop its Atlas V rocket on the launch pad earlier this month. (credit: NASA/Joel Kowsky)

Senior managers from NASA and Boeing told reporters on Friday that they plan to launch the first crew test flight of the Starliner spacecraft as soon as June 1, following several weeks of detailed analysis of a helium leak and a "design vulnerability" with the ship's propulsion system.

Extensive data reviews over the last two-and-a-half weeks settled on a likely cause of the leak, which officials described as small and stable. During these reviews, engineers also built confidence that even if the leak worsened, it would not add any unacceptable risk for the Starliner test flight to the International Space Station, officials said.

But engineers also found that an unlikely mix of technical failures in Starliner's propulsion system—representing 0.77 percent of all possible failure modes, according to Boeing's program manager—could prevent the spacecraft from conducting a deorbit burn at the end of the mission.

Enlarge / Boeing's Starliner spacecraft on the eve of the first crew launch attempt earlier this month. (credit: Miguel J. Rodriguez Carrillo/AFP via Getty Images)

The first crewed test flight of Boeing's long-delayed Starliner spacecraft won't take off as planned Saturday and could face a longer postponement as engineers evaluate a stubborn leak of helium from the capsule's propulsion system.

NASA announced the latest delay of the Starliner test flight late Tuesday. Officials will take more time to consider their options for how to proceed with the mission after discovering the small helium leak on the spacecraft's service module.

The space agency did not describe what options are on the table, but sources said they range from flying the spacecraft "as is" with a thorough understanding of the leak and confidence it won't become more significant in flight, to removing the capsule from its Atlas V rocket and taking it back to a hangar for repairs.

Enlarge / A view looking down at Boeing's Starliner spacecraft and United Launch Alliance's Atlas V rocket inside the Vertical Integration Facility at Cape Canaveral Space Force Station, Florida. (credit: United Launch Alliance)

Boeing is taking a few extra days to resolve a small helium leak on the Starliner spacecraft slated to ferry two NASA astronauts on a test flight to the International Space Station, officials said Tuesday.

This means the first crew launch of Boeing's Starliner spacecraft, running years behind schedule and more than $1.4 billion over budget, won't happen before next Tuesday, May 21, at 4:43 pm EDT (20:43 UTC). Meeting this schedule assumes engineers can get comfortable with the helium leak. Officials from Boeing and NASA, which manages Boeing's multibillion-dollar Starliner commercial crew contract, previously targeted Friday, May 17, for the spacecraft's first launch with astronauts onboard.

Boeing's ground team traced the leak to a flange on a single reaction control system thruster on the spacecraft's service module.