Jeff Bezos' Blue Origin filed a complaint after Elon Musk's SpaceX won a $2.9 billion contract to land astronauts on the moon
Elon Musk, Jeff Bezos
Elon Musk (L); Jeff Bezos
| Credit: Pascal Le Segretain/Getty; John Shearer/Getty

Warning: This post contains language that might be offensive to readers.

Jeff Bezos' Blue Origin filed a complaint on Monday after NASA selected Elon Musk's SpaceX for a multi-billion-dollar contract to send humans back to the Moon — and Musk has since responded on social media.

Blue Origin sent a 50-page complaint to the Government Accountability Office that accused NASA of "moving goalposts" for the companies competing for a $2.89 billion lunar lander contract to transport astronauts to the moon as early as 2024, which eventually went to SpaceX.

"NASA has executed a flawed acquisition for the Human Landing System program and moved the goalposts at the last minute," Blue Origin — which partnered with Lockheed Martin, Northrop Grumman and Draper in their bid to design the lander — says in a statement to PEOPLE. "In NASA's own words, it has made a 'high risk' selection."

"Their decision eliminates opportunities for competition, significantly narrows the supply base, and not only delays, but also endangers America's return to the Moon," the statement continues. "Because of that, we've filed a protest with the GAO."

SpaceX, NASA and the GAO did not immediately return PEOPLE's requests for comment.

In response to a New York Times reporter's tweet about the complaint, Musk mocked Bezos' Blue Origin, tweeting, "Can't get it up (to orbit) lol."

Musk also uploaded a picture of a Blue Origin moon-lander prototype that appeared edited to say "blue balls."

His initial tweet on the matter received over 45,000 likes as of Tuesday afternoon.

Musk is no stranger to making surprising comments on Twitter, where he has 52.1 million followers.

Before announcing the winner of their contract, it was expected that NASA would select two of the three companies to build the lander, the Washington Post reported. Doing so would help promote competition while ensuring a backup is in place if one company couldn't follow through with their concept — a typical NASA move, the newspaper explained.

According to Spaceflight Now, the U.S. space agency committed nearly $1 billion in funding to the lunar lander concepts, which was split between Blue Origin, SpaceX and Dynetics. But Blue Origin received $579 million of the funds, while SpaceX and Dynetics received $135 million and $253 million, respectively, according to Spaceflight Now and the Post. The newspaper reported that NASA indicated Blue Origin was furthest along last year.

RELATED VIDEO: SpaceX Launches Third Manned Mission to International Space Station

By picking SpaceX alone, NASA showed tremendous confidence in Musk's company, which has already worked with NASA to send astronauts to space — a feat its competitors have not yet accomplished.

SpaceX's third and most recent manned flight with NASA blasted off from Kennedy Space Center on Friday.

The lunar lander — whether it's made by SpaceX or Blue Origin — will be part of NASA's Artemis mission, which plans to put the first woman and next man on the Moon in 2024 and establish a sustainable human lunar presence by the end of the decade.