A Boeing official said Thursday that the company was “standing down” from an attempt to launch the Starliner spacecraft on July 21 to focus on recently discovered issues with the vehicle.

Mark Nappi, vice president and program manager for Starliner, said two spacecraft problems were discovered before Memorial Day weekend and that the company spent the holiday investigating them. After internal discussions that included Boeing chief executive Dave Calhoun, the company decided to delay the test flight that would carry NASA astronauts Suni Williams and Butch Wilmore to the International Space Station.

“Safety is always our top priority, and that drives this decision,” Nappi said during a teleconference with reporters.