Lockheed Martin's F-22 Raptor stealth fighter jet. Image source: Lockheed Martin.

Once upon a time, there was an F-22 Raptor. It was a good plane -- some even called it "the most capable air superiority combat jet in the world" -- but it cost a lot.

At a sticker price of $412 million per plane , the U.S. Air Force couldn't afford to buy a lot of F-22s. So, to ensure it had a good quantity of fighter jets, as well as a few of good quality, the Air Force proposed a "high-low" solution. On the high end, it would buy a handful of ultra-expensive F-22s to ensure air dominance. On the low end, to boost its numbers and ensure its ability to carry a lot of bombs into combat, it would buy a whole mess of F-35 Lightning II fighter jets -- projected to cost just $35 million each. (Lockheed Martin (LMT 0.84%), which builds both planes, was happy to oblige on both ends).

That was the plan. Instead, the F-35 fighter jet is turning out to be the most expensive fighter jet ever built, and is expected to ultimately cost taxpayers as much as $1.5 trillion.

Lockheed's F-35 -- the plane that was supposed to be cheap. Image source: Lockheed Martin.

How did we get it so wrong?
The story of Air Force's monumental miscalculation of the F-35's true cost is one that will go down in the history books -- and indeed, is already considered an historical fact. But the thing is, it was a miscalculation, and not an intentional misdirection.

As revealed in a piece that ran on DefenseOne last week, Lockheed Martin (and the Air Force) truly believed that the F-35 was going to be a (relatively) cheap plane to build, in part because the three F-35 variants desired by the U.S. Air Force, the Navy, and the Marine Corps were expected to share a large number of interchangeable parts.

In theory, each of the conventionally launched and landed F-35A, the vertical takeoff and landing F-35B, and the aircraft carrier-variant F-35C, were to use "common" parts. This commonality was supposed to save "billions of dollars" from not having to develop specialized parts for each F-35 variant and not having to maintain and run separate supply chains for each type of F-35. But as it turned out, the overlap among models is just 20%.

One more time, with feeling
As it worked out, as the F-35 program grew, the three "F-35" variants grew apart. And the effort to achieve commonality may have actually added to the cost of the program, while compromising each plane's ability to do its job well.

Characterizing these results after the fact, Air Force Lt. Gen. Christopher Bogdan says: "I'm not saying they're bad. I'm not saying they're good. I'm just saying they're hard." So as the Pentagon begins to make plans for its next-generation fighter jet, expected to enter service in the 2030s and dubbed "F-X" by the Air Force and "F/A-XX" by the Navy, there's a big incentive not to make the same mistake.

The implication being, it's looking increasingly likely that America's sixth-generation fighter jet will actually be several fighter jets, not one supposedly "common" system.

What it means to investors
For several reasons, that might not be a bad thing. First and foremost, if cost savings from a common system have proved illusory, there's little incentive to try to do something that's "hard" -- and probably doomed to fail. Taxpayers should applaud a move by the military to learn from past mistakes.

Second, taking the easier route of building a fighter tailor-made for what the Air Force needs -- and a second plane for the Marines, and a third for the Navy -- offers the prospect of multiple defense contractors winning work. Each of Lockheed Martin, Boeing (BA 1.44%), and Northrop Grumman (NOC -0.33%) could compete for these contracts, preserving price competition and driving costs down. And in the end, each contractor could still win a big chunk of business, building the planes it builds best.

And there's a third reason this could be good news for defense contractors, and for the shareholders who invest in them: The Pentagon's past preference for gargantuan-budget, winner-take-all competitions for "common" weapon systems has spawned a rising plague of lawsuits in the defense industry. No sooner does a company win a contract than it's immediately hit with lawsuits from the losers, hoping to steal that contract away from it.

Granted, these lawsuits generally fail, but they cost money, delaying the acquisitions process. Giving more companies a fairer shake at winning work might do a lot to make the whole process go more smoothly and -- judging from the F-35's record -- maybe more successfully, too.

Lockheed Martin's F-35 program -- upside down in so many ways. Image source: Andy Wolfe for the U.S. Navy.