Not so fast, Boeing Starliner. Boeing’s first crewed spaceflight was scheduled to launch Monday night from Space Launch Complex 41 at Florida’s Cape Canaveral Space Force Station, but it was postponed just two hours before liftoff. Astronauts Suni Williams and Butch Wilmore were on board and ready to fly when the launch was called off. On Tuesday, NASA said that the earliest the launch would happen would be Friday, May 10.

The mission was scrubbed because of a faulty oxygen relief valve on the Atlas V rocket that was set to send the Starliner capsule into space. The valve was «buzzing,» or opening and closing rapidly, during the launch countdown, Space.com reported.

The Atlas V rocket was created by the United Launch Alliance, which is a joint venture between Boeing and Lockheed Martin. 

NASA says the mission will take the astronauts to the International Space Station for a little over a week, to test the Starliner spacecraft and its subsystems. The testing is the final step in certifying the Starliner for repeat use in transport missions to and from the ISS. Once it finally launches, the Starliner should reach the ISS approximately 26 hours after launch.

This is the first new spacecraft to head to the ISS since the SpaceX Demo-2 made the same voyage back in 2020. The Boeing Starliner started life in 2010, when it was selected by NASA to be the next reusable transport to the ISS.

«The arrival of a brand-new vehicle, the first crewed flight of a new-generation spacecraft, is a really big deal,» said Michael Barratt, one of seven residents of the ISS. «You leave nothing to chance.»

A mission 14 years in the making

The Starliner was initially conceived as a commercial effort to take more people into space. In 2014, NASA tapped Boeing and SpaceX, and chose Starliner to be one of the first privately constructed spacecraft to shuttle astronauts to the ISS. NASA wanted to lean more on private business to build and maintain such spacecraft, instead of performing all the work itself. 

Test flights were delayed for several reasons, ranging from unfavorable weather conditions to problems with software. Tests were pushed back in 2019 and again in 2021, and eventually were delayed till 2022. 

The unmanned test flight finally launched on May 19 of that year, with the mission wrapping up a week later. It was a huge win for the Boeing crew, since it opened the doors for a crewed mission to the space station. NASA was pretty pumped about it as well. But the crewed launch was pushed back because of various problems, including some with the Atlas V rocket that’s presenting the problem with the 2024 launch.

The spacecraft is part of NASA’s Commercial Crew Program, which is connected to its Artemis and moon to Mars plans. 

How to watch the Boeing Starliner launch — eventually

NASA had planned to livestream Monday’s event on its YouTube channel, with commentary by Spaceflight Now’s Will Robinson-Smit. The direct video link is here, but of course the livestream is on hold until it happens.

Other YouTube channels had also planned to livestream the event, including SpaceX, Space.com’s VideoFromSpace channel and the Associated Press YouTube channel. We’ll update this story, and the video links, when a new launch date and time are announced.

CNET’s Gael Cooper contributed to this article.