Elon Musk has emerged victorious in the latest battle of the space fat-cats after Jeff Bezos's multi-billion dollar contract challenge was turned down.
In April, Musk's SpaceX was awarded a US$2.9 billion deal by NASA to become the single lunar lander provider for the agency with the aim of delivering astronauts to the moon as early as 2024.
Both Bezos's Blue Origin and defense contractor Dynetics were unhappy with the decision and protested, believing two providers should be chosen - but have been turned down by the US Government Accountability Office (GAO).
Blue Origin said NASA had failed to allow SpaceX's competitors to "meaningfully compete for an award when the Agency's requirements changed due to its undisclosed, perceived shortfall of funding for the multi-year programme lifecycle".
But the GAO denied the arguments that NASA acted improperly in making a single award to SpaceX, drawing a "GAO" tweet from Musk which also contained the muscle flex emoji.
The decision came just days after Bezos offered NASA a US$2 billion discount to give a contract to Blue Origin instead of SpaceX.
In an open letter to NASA administrator Bill Nelson he backed his company to make a lander capable of returning astronauts to the surface of the moon.
"I believe this mission is important. I am honoured to offer these contributions and am grateful to be in a financial position to be able to do so," he wrote.
"NASA veered from its original dual-source acquisition strategy due to perceived near-term budgetary issues, and this offer removes that obstacle."
But that has failed to make any impact on the GAO, while the company remains convinced there were fundamental issues with the decision. It said it will continue to push for two providers as the best solution.
When the decision was announced, NASA said that sending astronauts to the moon was a priority for the Biden Administration - and that could now move forward.
"GAO's decision will allow NASA and SpaceX to establish a timeline for the first crewed landing on the moon in more than 50 years," NASA said in a statement.
When news of Blue Origin's protest - which ran to 175 pages - was first revealed, Musk trolled Bezos with a tweet saying "Can't get it up (to orbit) lol."
The last moon landing mission was Apollo 17 in 1972 during which Commander Eugene Cernan and Lunar Module pilot Harrison Schmitt walked on the lunar surface.