Blue Origin filed a federal lawsuit Friday to challenge a NASA moon landing contract awarded solely to rival company SpaceX, upping the ante in an already tense standoff over the multibillion-dollar lunar lander program. The protective order was first publicly posted Monday. Details of the lawsuit are not publicly available because the documents are under seal, but Blue Origin claims it is an “attempt to remedy the flaws in the acquisition process found in NASA’s Human Landing System,” the company said in a statement. Human Landing System, or HLS, is the formal name of the program that’s at the heart of this legal battle, and it seeks to use private-sector contracting to develop, build and test the vehicle that will put astronauts on the moon for the first time in a half-century. After initially pledging to offer multiple contracts to spur the development of at least two lunar landers that could compete against each other, NASA announced in April that it was giving only a single award to SpaceX for $2.9 billion, citing costs as a primary reason for the decision. Congress did not award NASA all the money it had requested for the HLS program. Blue Origin previously attempted to fight the contracting decision with the US Government Accountability Office, but the GAO sided with NASA and denied the request. “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 in a statement. A statement from NASA sent to reporters Monday evening said the agency was “notified” of the claims Blue Origin made in court and is “currently reviewing details of the case.” “As soon as possible, the agency will provide an update on the way forward for returning to the Moon as quickly and as safely as possible under Artemis,” the NASA statement reads, using the name of the moon landing program of which HLS is part. A judge granted Blue Origin’s request to keep the court complaint under seal, which argued that making the information public could expose “proprietary information, trade secrets, and confidential financial information,” and cause “severe competitive harm,” according to court documents file with the US Court of Federal Claims. The warring between SpaceX and Blue Origin — which are owned by two of the world’s richest men, Elon Musk and Jeff Bezos, respectively — has also included a public PR battle. Blue Origin has called SpaceX’s plans to use its Starship vehicle, a massive experimental rocket being tested in South Texas, for the HLS program “immensely complex and high risk.” SpaceX CEO Musk, meanwhile, has disparaged Blue Origin’s claims on Twitter for weeks, at one point saying that “If lobbying & lawyers could get u to orbit, [Blue Origin CEO Jeff] Bezos would be on Pluto [right now.]” Blue Origin had submitted a $5.9 billion bid and proposed working as a “National Team” alongside aerospace industry giants such as Northrop Grumman and Lockheed Martin.