Elon Musk criticized the F-35 program on Sunday. Musk's comments come as he prepares to advise Trump on government efficiency in 2025.The GAO expects the F-35 program to cost about $2 trillion over its entire lifespan.Elon Musk, who's set to start advising President-elect Donald Trump on government efficiency in 2025, criticized the Pentagon's F-35 program in two brief social media posts on Sunday.The billionaire reposted a video montage of coordinated drone swarms on X, writing: "Meanwhile, some idiots are still building manned fighter jets like the F-35."He added a "trash can" emoji to his post. When another X user defended the F-35's capabilities, Musk responded that the prized jet is a "shit design."It's unclear if Musk intends to use his new position to impact any plans or costs for the F-35, the Pentagon's most expensive fighter program to date.But he mentioned Defense Department spending in a column in The Wall Street Journal that criticized federal government budgets."The Pentagon recently failed its seventh consecutive audit, suggesting that the agency's leadership has little idea how its annual budget of more than $800 billion is spent," Musk wrote in the column with Vivek Ramaswamy, who is to lead Trump's new Department of Government Efficiency with him.Musk and Ramaswamy wrote that the intention of their department is to eliminate the "sheer magnitude of waste, fraud, and abuse that nearly all taxpayers wish to end."As for the F-35, costs for the Lockheed Martin-developed stealth jet have hit about $485 billion, after a 10% bump this year due to what the Pentagon said was a need to improve its engine cooling.Around 1,000 of the planes have been delivered to the US military and its allies, out of a total of over 3,000 aircraft planned for production over the F-35 program's lifetime.The jet's operational lifespan is estimated to last until 2088, and the Government Accountability Office thus expects the F-35 program to cost over $2 trillion to produce and sustain.Musk, the Pentagon, and Lockheed Martin did not respond to requests for comment sent outside regular business hours by Business Insider.Musk has said before that the US should consider remote-piloted alternatives to manned jets, both to keep up with the rise in drone warfare but also to help Air Force procurement stay competitive."The competitor should be a drone fighter plane that's remote controlled by a human, but with its maneuvers augmented by autonomy. The F-35 would have no chance against it," Musk tweeted in February 2020.In response to Musk's tweets, a Lockheed Martin spokesperson told Fortune that the F-35 is "the most advanced, survivable, and connected fighter aircraft in the world, a vital deterrent and the cornerstone of joint all-domain operations."As we did in his first term, we look forward to a strong working relationship with President Trump, his team, and also with the new Congress to strengthen our national defense," they added.A Pentagon spokesperson also told the outlet: "We have combat-capable aircraft in operation today and they perform exceptionally well against the threat for which they were designed. Pilots continually emphasize that this is the fighter they want to take to war if called upon.""In the next 10 years, there will be 700 F-35s in Europe and only 60 of these will belong to the US," they also said.