Enlarge / A view looking down at Boeing's Starliner spacecraft and United Launch Alliance's Atlas V rocket inside the Vertical Integration Facility at Cape Canaveral Space Force Station, Florida. (credit: United Launch Alliance)

Boeing is taking a few extra days to resolve a small helium leak on the Starliner spacecraft slated to ferry two NASA astronauts on a test flight to the International Space Station, officials said Tuesday.

This means the first crew launch of Boeing's Starliner spacecraft, running years behind schedule and more than $1.4 billion over budget, won't happen before next Tuesday, May 21, at 4:43 pm EDT (20:43 UTC). Meeting this schedule assumes engineers can get comfortable with the helium leak. Officials from Boeing and NASA, which manages Boeing's multibillion-dollar Starliner commercial crew contract, previously targeted Friday, May 17, for the spacecraft's first launch with astronauts onboard.

Boeing's ground team traced the leak to a flange on a single reaction control system thruster on the spacecraft's service module.