– Pentagon leaders and thousands of military contractors across the country might be wondering just what President-elect Donald Trump has in store for them.

In two tweets this month that sent shock waves through defense companies and their lobbying firms, Trump criticized the spiraling costs of building a new Air Force One and a fleet of F-35 fighter jets.

That criticism triggered meetings a week ago with the heads of those two projects’ main manufacturers, Boeing Co. and Lockheed Martin Corp., at the billionaire’s Mar-a-Lago resort in Palm Beach, Fla. Trump said afterward that he’d extracted promises to cut costs.

But it remains to be seen whether Trump will be able to stay on top of Pentagon excess after he becomes president Jan. 20. The day after Trump met with the leaders of the two defense contractors, the Pentagon announced a long list of spending projects that totaled nearly $550 million.

Trump will have a difficult time focusing on that wide range of spending and carrying out his pledge to pay for expanded military operations by trimming Pentagon waste, say experts on the way the Pentagon oversees its contracts. He won’t find many friends in the process, they note.

“He’s going to encounter a Pentagon bureaucracy that will instinctively say ‘no’ to most reforms he proposes,” said Todd Harrison, a former defense lobbyist and retired Air Force Reserves captain. “He’s certainly not the first president to come in saying we can cut waste and abuse within the Pentagon budget. Very few have had much success.”

William Hartung, who in 2011 wrote a book about the clout F-35 contractor Lockheed Martin wields in the U.S. Congress, made a similar observation about the Pentagon.

“They don’t scrutinize the original bids carefully enough, so contractors come in with a low bid while understanding that they’re not going to meet it,” Hartung said. “And then the Pentagon will add requirements and new features along the way. Eventually the costs get out of control.”

By the time that’s evident, however, inertia keeps the program going. “Once they put a certain amount of money on the table, they’re reluctant to end or dramatically scale it back,” Hartung said.

Whether Trump will be able to change that culture is what experts in Pentagon procurement are watching. With a price tag of $400 billion and rising, the F-35 Joint Strike Fighter, for example, already is the most expensive weapons system ever built. It could end up exceeding $1 trillion by the time all planned 2,457 planes are manufactured.

The pre-inaugural meetings with the defense firm bosses give Harrison some grounds to hope. The meeting is in keeping with Trump’s penchant for the unconventional approach.

Afterward, Boeing CEO Dennis Muilenburg pledged to get Air Force One built for less than the $4 billion budgeted. Lockheed Martin’s CEO Marillyn Hewson was less committal, pledging only that her company is dedicated to “delivering an affordable aircraft to our U.S. military and our allies.”

“I think he will be less likely to listen to the bureaucracy,” Harrison said of Trump. “What we’ve seen so far is that he’s more self-confident and he’s willing to say things and do things that buck the establishment. He almost takes joy in it.”