Jeff Bezos’ space company Blue Origin filed a complaint in federal court against NASA, continuing its protest that the agency wrongly awarded a lucrative contract to Elon Musk’s SpaceX earlier this year.

“This bid protest challenges NASA’s unlawful and improper evaluation of proposals,” Blue Origin’s lawyers wrote in its court filing.

The protest, filed in the U.S. Court of Federal Claims on Monday, is sealed and marks the next step in the company’s attempt to get NASA’s decision overturned. A Blue Origin spokesperson confirmed the lawsuit filing, adding in a statement to CNBC that it is looking “to remedy the flaws in the acquisition process found in NASA’s Human Landing System.”

“We firmly believe that the issues identified in this procurement and its outcomes must be addressed to restore fairness, create competition, and ensure a safe return to the Moon for America,” Blue Origin said.

Blue Origin’s filing in court comes a couple of weeks after the U.S. Government Accountability Office denied the company’s protest, upholding NASA’s decision.

The GAO ruling backed the space agency’s surprise announcement in April that NASA awarded SpaceX with a lunar lander 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.

Blue Origin has not let up on its fight to win a contract under NASA’s HLS 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 April 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.

The company’s court filing on Monday comes as Blue Origin has stepped up a public relations offensive against NASA using SpaceX’s next-generation Starship to land astronauts on the moon. In a series of comparative infographics, Blue Origin has emphasized the “unprecedented number of technologies, developments, and operations that have never been done before for Starship to land on the Moon.”

Blue Origin last week released an infographic last week that added that Starship is “a launch vehicle that has never flown to orbit and is still being designed.”

Musk, in response to Blue Origin’s infographic, gave his view of Bezos’ company and its criticism.

“The sad thing is that even if Santa Claus suddenly made their hardware real for free, the first thing you’d want to do is cancel it,” Musk wrote in a tweet.