FIGHTER DEMONSTRATION CENTER, ARLINGTON, VA: Lockheed Martin executives gathered to tout their F-35 Joint Strike Fighter dismissed a widely reported Pentagon estimate that the aircraft would ultimately cost $1.1 trillion to develop, build, and operate over 55 years. In fact, they argued, the F-35 will cost less to operate than the airplanes it will replace — a highly controversial claim.

“Lockheed Martin believes this aircraft is going to be about the same or even less to operate over the life of the program,” said Robert Rubino, a former Navy pilot who now heads the Navy portion of the Lockheed F-35 program. In the DoD estimate, he said, “they were using legacy data, legacy models” that don’t account for how the F-35 was designed with ease of maintenance and affordability in mind: “They don’t give credit for any of those enhancements.”

Stealth aircraft are notoriously expensive to maintain, with the radar-absorbing coatings on the B-2 prone to disintegrate in the rain, but Rubino argued that F-35 is a different animal. “We have learned a whole lot over the last 20 years as far as maintaining stealth,” he said. “We built this airplane to be able to have very robust stealth, to the point where you can ding it, you can scratch it” and it does not lose its radar-evading properties.

Even if you dismiss Lockheed’s claims about F-35′s maintainability, there are still serious questions about the Pentagon’s methodology. To get the trillion-dollar figure, Defense Department cost estimators did something they’ve never attempted before, Rubino told reporters: They tried to calculate the entire cost of the F-35 program, from initial R&D spent years ago, through production now just getting underway, to the cost of the last flight flown by the last F-35 before it is retired sometime in 2065. That includes such variables as the price of fuel, which is hard to predict month to month, let alone 50 years out. Worst of all, the $1.1 trillion is in “then-year” dollars, which means it counts the impact of five decades of inflation. Air Force magazine estimated that just putting the bill in 2011 dollars would cut it in half.

Even if you take the trillion-dollar figure at face value, added Steve Callaghan, the F-35 director in Lockheed’s Washington office, “is that a good number or a bad number? It inherently sounds like it’s a big bad number, but not necessarily when you look at the alternatives.” Applying the same accounting methodology to the planes F-35 is to replace, he said, “if you could take all these legacy airplanes and push them forward 55 years, we think a conservative number is about four times more than to operate the F-35.”

Of course, Callaghan added, “you really can’t keep these airplanes another 55 years”: They’d physically fall apart long before then — which is the reason the Air Force in particular is desperate to field new planes. Even in the near term, aging aircraft get more expensive to maintain with every passing year, and most of the current air fleet was built during the Reagan buildup.

Lockheed has a point when it argues that projecting operating costs from now to 2065 is an inherently unreliable exercise. But what about something simpler, the cost per flight hour in the near term?

The current Defense Department objective is that the vanilla F-35A, the Air Force model, will cost no more than $35,200 per flight hour, which is still a whopping 56 percent more than the $22,500 per flight hour of the F-16 it’s supposed to replace. (This time, by the way, both figures are are 2012 dollars). But former GAO analyst and sometime Breaking Defense contributor Winslow Wheeler argues even that figure is optimistic.

“[C]omparing the F-35 to the F-16 is a major error,” Wheeler wrote on the Time defense blog, Battleland. “The F-35A has much more in common with its Lockheed stablemate, the F-22” — the F-22 is a lot larger, but Wheeler argues the F-35 in some respects even more technologically complex — so the F-22 should be the starting point for cost comparisons instead.

The F-22 cost $63,929 per flight hour in 2010, Wheeler wrote, and while F-35 will be less, it won’t be as low as the Pentagon hopes. His guesstimate: F-35 will cost $51,143 per flight hour, 20 percent less to operate than the F-22, but more than double the F-16.

Wheeler is an ardent critic of the F-35 and Pentagon procurement generally, so his estimates are inclined to pessimism, just as Lockheed’s are inclined to optimism. But whoever’s right, the cost to buy and then operate this airplane will be a major burden on defense budgets for decades to come.