United Launch Alliance said Monday it did not submit a proposal in a competition to launch a U.S. Air Force GPS navigation satellite, apparently relinquishing the contract to rival SpaceX, the only other company certified to launch the mission.

Boeing and SpaceX hope to launch commercial crew ferry ships on long-awaited test flights later this year, but both companies face major challenges getting the spacecraft certified before late 2019 when seats aboard Russian Soyuz spacecraft will no longer be easily available for NASA space station crews, officials told lawmakers Wednesday.

United Launch Alliance’s first Vulcan rocket was filled with methane and liquid oxygen propellants at Cape Canaveral last week for a tanking test, but managers decided to move the rocket back inside a hangar for a few adjustments before proceeding with an engine test-firing.