Photos: Atlas 5 rollout

The head of NASA’s human spaceflight programs has abruptly resigned, announcing his departure from the space agency two days before before he was to chair a crucial readiness review ahead of the launch of the first crewed U.S. space mission in nearly a decade.

The rollout operation on Tuesday followed a day of evaluations using Boeing’s weight and center-of-gravity machine to determine the final measurements on the spacecraft. Launch is still targeting May 6 at 10:34 p.m. EDT (0234 UTC).

SpaceX’s proposal to land astronauts on the moon using the company’s reusable Starship vehicle could be “game-changing” for space exploration, but comes with risks and complexity that “threaten the schedule viability” to achieve NASA’s goal of returning crews moon by the end of 2024, agency officials said.