Thanks to the sequester, the Defense Department is now required to cut more than $40 billion this fiscal year out of its $549 billion budget. But one program that's unlikely to take a significant hit is the F-35 Joint Strike Fighter, despite the fact that it's almost four times more expensive than any other Pentagon weapons program that's in the works.

We've compiled some of the most headache-inducing figures, from the program's hefty cost overruns to the billions it's generating in revenue for Lockheed Martin.

While the F-35 is billions over budget and years behind schedule, the program seems to be doing better recently. A Government Accountability Office report released this week found that Lockheed has made progress in improving supply and manufacturing processes and addressing technical problems.

"We've made enormous progress over the last few years," Steve O'Bryan, Lockheed’s vice president of F-35 business development, told the Washington Post.

The military’s current head of the program, Lt. Gen. Christopher Bogdan, agreed that things have improved but said Lockheed and another major contractor, Pratt & Whitney, still have a ways to go.

“I want them to take on some of the risk of this program,” Bogdan said last month in Australia, which plans to buy 100 of the planes. “I want them to invest in cost reductions. I want them to do the things that will build a better relationship. I’m not getting all that love yet.”

Correction: An earlier version of this post included the estimated total cost of the F-35 program when it began in 2001 ($233 billion) as well as an inflation-adjusted figure calculated in 2013 dollars in parentheses. The $233 billion figure, however, already included projected inflation, so we have removed the inflation-adjusted figure.