They also warned that since this was a test flight to and from the International Space Station, everything might not go perfectly.

Instead of coming home after about eight days, the spacecraft remains docked to the station, its return delayed indefinitely while teams continue to troubleshoot a series of problems -- helium leaks and a few thrusters that stopped working at a critical moment in the flight -- in the capsule's propulsion system.

While the top priority is making sure NASA astronauts Sunita Williams and Barry "Butch" Wilmore return to Earth safely, the technical delays, and whether Boeing can overcome them, reflect not only the high stakes for the future of the Starliner program, but also the company's future in space. Boeing desperately needs to demonstrate that it can fly astronauts safely and overcome the kinds of technical challenges that have been plaguing the spacecraft, as well as the company's commercial aviation division.

Once the mission is complete, NASA and Boeing must undergo a rigorous process to certify Starliner for regular crew rotation missions with a full contingent of four astronauts for regular six-month stays on the station. Only then can Starliner join SpaceX's Dragon, which first flew astronauts for NASA in 2020, and deliver on a $4.2 billion contract NASA awarded Boeing a decade ago.

NASA is eager for Boeing's Starliner to serve as a second American transportation system to the space station. SpaceX has been serving that function alone since 2020, but NASA says it needs two systems in case one goes down.

Years of setbacks, including a botched test flight without astronauts on board in 2019, have cost Boeing some $1.5 billion in cost overruns. It needs Starliner to start flying the regular crew rotation flights so that it can start getting paid for the missions.

Starliner has sprung a series of small helium leaks that have confounded NASA and Boeing and have led to a number of delays in getting off the ground and then coming home. Originally, the teams said they thought the leaks were due to a bad seal, but they later said they were not sure what was behind them. They are also trying to figure out why five of the spacecraft's small thrusters suddenly stopped working as the spacecraft approached the space station on June 6, forcing NASA to have Boeing back up the vehicle and refire the thrusters to bring them back online.

Initially, Starliner was supposed to come home June 18; then NASA pushed that back to June 26. The space agency delayed it again Friday to sometime later in July, saying the teams needed more time to study the propulsion system problems.

There is no rush to fly the astronauts home, NASA said; the helium leaks don't pose a risk to the return, it has said. Four of the five thrusters are now operating normally, and since the spacecraft is outfitted with 28 such thrusters, there is plenty of redundancy, officials have said. The spacecraft can stay docked in space for up to 45 days, giving crew members a little breathing room to continue to troubleshoot the issues.

NASA and Boeing have repeatedly stressed that Starliner is healthy and could be used at any time to fly the astronauts back to Earth in the case of an emergency on the space station.