Boeing’s Starliner capsule is leaving the launchpad after a series of delays that prevented takeoff over the last few days. NASA and the beleaguered aerospace giant will take “whatever time is necessary” to find and fix the issue, but it’s beginning to feel like this long-in-development spacecraft may never make it to the ISS.

This the second major launch attempt after the Starliner failed to enter the correct orbit in a 2019 launch. The rescheduled ISS rendezvous launch was originally scheduled for March of this year, but eventually delayed to this week. A valve issue prompted a countdown halt yesterday, but the ground teams have been unable to resolve the problem as the whole operation has had to stand down as a result.

“Engineering teams have ruled out a number of potential causes, including software, but additional time is needed to complete the assessment,” wrote NASA in a news release. “Mission teams have decided to roll the Atlas V and Starliner back to the Vertical Integration Facility (VIF) for further inspection and testing where access to the spacecraft is available. Boeing will power down the Starliner spacecraft this evening.”

It’s another major setback for Boeing’s shot at providing crew launch capability, something its rival SpaceX has achieved now multiple times despite originally working on a very similar timeline. Both experienced years of delays, but ultimately Crew Dragon was successfully piloted to the ISS while Starliner is yet to make a successful orbital trip at all, let alone one with astronauts on board.

Some may wonder whether this is throwing good money after bad, since the race is apparently lost. But Boeing knows better than many that this is a marathon, not a sprint, and that the demand for orbital launches is nearly insatiable. Even if SpaceX has a multi-year lead on Boeing, Boeing has a multi-year lead on some of its other competitors and if it can get Starliner working there will likely be enough customers to make even its tortuous development worthwhile.

Depending on how quickly this valve issue is resolved, it could be weeks or months before there’s another launch attempt.