NASA astronauts
NASA astronauts Butch Wilmore and Sunita Williams walk at NASA's Kennedy Space Center, ahead of Boeing's Starliner-1 Crew Flight Test (CFT) mission. Image Credit: Reuters

Boeing Co. and NASA will again try to launch the first crew to orbit on the company's long-delayed space taxi following a helium leak delay last month.

The company's spacecraft, the CST-100 Starliner, is set to take off on Saturday from Cape Canaveral, Florida, at 12:25 p.m. local time. It will carry NASA astronauts Sunita "Suni" Williams and Barry "Butch" Wilmore to the International Space Station where they will attempt to dock around midday Sunday for a roughly week-long stay.

Saturday's flight is a critical test for NASA to prove Starliner can safely carry people to and from the ISS under the US space agency's Commercial Crew Program. In 2014, NASA awarded Boeing $4.2 billion and Elon Musk's SpaceX $2.6 billion in contracts to create vehicles to ferry the agency's astronauts to space.

While Starliner has fallen seven years behind schedule due to a long line of technical glitches and failures, SpaceX has launched nine separate crews to the space station for NASA since 2020.

The repeated delays have added mounting pressure for Boeing, which has racked up roughly $1.5 billion in cost overruns on the program. The company's defense and space division is expected to lose money during the second quarter, Chief Financial Officer Brian West told a conference in May, citing "cost pressure" on fixed-price contracts.

No matter what happens with this launch, Boeing faces questions about the long-term vision for its space business. It's unclear whether Starliner will be used beyond a half-dozen more missions to the ISS for NASA. Late last year, West told a small gathering of investors that the company has a decision to make about future investment in the program, Bloomberg has reported.

The Saturday launch target comes after weeks of uncertainty about when this mission would get off the ground. NASA and Boeing tried to launch on May 6, but mission controllers stopped the countdown after noticing some weird behavior with a valve inside the rocket, forcing Williams and Wilmore to exit the spacecraft and wait for another launch day.

Engineers replaced the valve, but the launch was delayed again after Boeing discovered a helium leak on one of Starliner's many thrusters. After weeks of analysis and meetings, Boeing and NASA ultimately decided to move forward with the launch without fixing the leak, saying it did not pose a safety issue and that engineers would monitor it throughout the flight.

"We could handle up to four more leaks, and we could handle this particular leak if that leak rate were to grow even up to 100 times," Steve Stich, NASA's manager for the agency's Commercial Crew Program, said at a news conference.

It's possible that the fresh launch delays will force Boeing to take another incremental charge on Starliner, JPMorgan analyst Seth Seifman said in a May 27 research note.

If Starliner is able to successfully dock with the space station, Williams and Wilmore will stay aboard about a week. The crew has tentative plans to return to Earth as early as June 10 inside Boeing's space taxi, which is set to land in the southwestern United States under parachutes.