The U.S. Government Accountability Office on Friday denied protests from companies affiliated with Jeff Bezos that NASA wrongly awarded a lucrative astronaut lunar lander contract solely to Elon Musk’s SpaceX.

The complaints were filed by Jeff Bezos’ Blue Origin and Leidos’ subsidiary Dynetics.

“NASA did not violate procurement law or regulation when it decided to make only one award … the evaluation of all three proposals was reasonable, and consistent with applicable procurement law, regulation, and the announcement’s terms,” GAO managing associate general counsel Kenneth Patton wrote in a statement.

The GAO ruling backs the space agency’s surprise announcement in April that NASA awarded SpaceX with a contract worth about $2.9 billion. SpaceX was competing with Blue Origin and Dynetics for what was expected to be two contracts, before NASA only awarded a single contract due to a lower-than-expected allocation for the program from Congress.

SpaceX, Blue Origin, Dynetics, and NASA did not immediately respond to CNBC’s request for comment.

The GAO protest ruling resolves a dispute around NASA’s Human Landing System program, one of the final key pieces of the agency’s plan to return U.S. astronauts to the surface of the moon.

Before the most recent contract award, NASA had handed out nearly $1 billion in concept development contracts – with SpaceX receiving $135 million, Dynetics 253 million, and Blue Origin receiving $579 million.

In choosing SpaceX for the next round of development, NASA decided to fund a variation of SpaceX’s Starship rocket, prototypes of which SpaceX has been testing at its development facility in Boca Chica, Texas. 

NASA plans for its astronauts to use Starship to transfer from the agency’s Orion spacecraft when the capsule reaches lunar orbit.

Shortly after NASA’s announcement in April, Blue Origin and Dynetics each filed protests with the GAO, challenging the space agency’s process and decision.

Blue Origin in April decried the award as “flawed,” saying that NASA “moved the goalposts at the last minute.”

The company also revealed that its proposal was roughly double that of SpaceX, with a bid of $5.99 billion. NASA later revealed that Dynetics’ bid was even higher, at $8.5 billion.

Shortly after flying himself to space on Blue Origin’s first crewed flight, Bezos wrote in a letter to NASA earlier this week that he would cover as much as $2 billion in the space agency’s costs for a lunar lander contract.

“We stand ready to help NASA moderate its technical risks and solve its budgetary constraints and put the Artemis Program back on a more competitive, credible, and sustainable path,” Bezos wrote in the letter.

The billionaire’s letter did not reference what would happen to that counteroffer if the GAO upheld NASA’s decision.