After a wave of whistleblowers and a new FAA probe, the planemaker has abandoned its plans for its first crewed launch of the Starliner spacecraft "out of an abundance of caution," just two hours before planned takeoff.

The United Launch Alliance (ULA) cites an issue with the oxygen relief valve on the Atlas V rocket for scrubbing the launch.

Officials involved in the planned launch had said repeatedly that they wouldn't hesitate to postpone the flight if any risks to safety emerged. Bill Nelson, the administrator for NASA and a former astronaut himself, reiterated that point Monday evening, saying the agency's first priority is safety.

"We go when we're ready," he said in a post on X.

Seven years behind schedule and more than a billion-dollar cost overrun, Boeing's Starliner spacecraft is finally atop an Atlas V rocket at Florida's Cape Canaveral Space Force Station. If all goes according to plan, the launch will occur tonight at 2234 ET.