There are big air shows in the UK this summer. The British public may be a little disappointed, however. The F-35B Joint Strike Fighter—the stealth jet that’s supposed to be able to take off and land vertically, like a helicopter—will be on display for the first time outside the U.S. But it won’t emulate the vertical landings that the Harrier family has made routine since the Beatles were playing dodgy nightclubs in Hamburg.

U.S. Marine aviation boss Brig. Gen. Matthew Glavy has said that there are no plans for the F-35B to perform vertical landings (VLs) in the UK, because the program has not finished testing the matting that’s needed to protect the runway from exhaust heat. (The program office, the Marines, and Lockheed Martin did not return emails about any part of this story.) It may sound like a simple issue, but it pops the lids off two cans of worms: the program’s relationship with the truth, and the operational utility of VL.

The F-35B—the version of the Joint Strike Fighter that the Marines and the British are buying—is designed to take off in a few hundred feet and land vertically, like a helicopter. Its advocates say that will allow the Marines to use short runways worldwide as improvised fighter bases, providing air cover for expeditionary forces. But to do VL, the engine thrust must be pointed straight downward, and the jet is twice the size of a Harrier. Result: a supersonic, pulsating jackhammer of 1,700-degree F exhaust gas.

In December 2009, the Naval Facilities Engineering Command (Navfac) issued specifications for contractors bidding on JSF construction work. The main engine exhaust, the engineers said, was hot and energetic enough to have a 50% chance of spalling concrete on the first VL. (“Spalling” occurs when water in the concrete boils faster than it can escape, and steam blows flakes away from the surface.)

Lockheed Martin, the lead contractor on the F-35B, was dismissive. The specifications were out of date and based on worst-case assessments, the company said, and tests in January 2010 showed that “the difference between F-35B exhaust temperature and that of the AV-8B [Harrier] is very small, and is not anticipated to require any significant… changes” to how the new plane was operated.

Navfac ignored Lockheed Martin and commissioned high-temperature-concrete VL pads at four sites. At the Navy’s Patuxent River flight test center, F-35Bs perform VLs on a pad of AM-2 aluminum matting, protecting the concrete from heat and blast. Why didn’t the January 2010 tests result in a change to the specifications? How were those tests performed? The Navy has referred those questions to Lockheed Martin, which has repeatedly failed to answer them.

This isn’t the only instance where Lockheed Martin has tried to shoot the messenger on the basis of weak facts. Last year, the Rand Corporation in a report concluded that the JSF—a program that incorporates three variants of F-35, each one for a different military service—will cost more than three single-service programs would have done. Lockheed Martin accused Rand of using “outdated data,” but founded that criticism on numbers that were not in the report.

One reason the F-35 program is running behind schedule is that Pentagon overseers forced Lockheed Martin and the program office to reinstate flight tests that they had cut out, a move that the current program manager thinks was necessary. But Lockheed Martin consultant Loren Thompson accused Pentagon testing experts of “wanting the opportunity to close out their home mortgages and get that last kid through college.”

After a 2011 report showed the F-35A cost per flight-hour to be 40 percent higher than the F-16’s, program leaders asserted that the Pentagon’s accountants had misinterpreted their own numbers. Three years later, the numbers have barely budged.

The bigger issue is that the Pentagon bought the F-35B for two reasons: it can land on an LHA/LHD-class amphibious warfare ship, and it can operate from an improvised forward operating location, created around a 3,000-foot runway. The capabilities are complementary. Without one of those forward operating locations, the amphibious force is limited to six fighters per LHA (unless essential helicopters are off-loaded). But a short runway is of little value unless you can use it twice.

And what Navfac calls “standard airfield concrete” is military-grade, made with aggregate and Portland cement. Many runways are asphaltic concrete—aggregate in a bitumen binder—which softens and melts under heat.

The Marines could use AM-2 landing pads. But AM-2 is not a friend to the agility that justifies the F-35B over other forms of expeditionary airpower. An Air Force study calls it “slow to install, difficult to repair, (with) very poor air-transportability characteristics.” A single 100- by 100-foot VL pad weighs around 30 tons and comprises 400 pieces, each individually installed by two people.

At the very least, that will add to the challenges of operating a complex 25-ton fighter—twice as big and fuel-thirsty as the Harrier it replaces—under canvas and off the grid, particularly in a hybrid-war situation where supplying a squadron by land may be hazardous or impossible.

Rolling or creeping vertical landings can spread the heat load over a greater area. But there is no sign that they have been tested on concrete, asphalt, or AM-2 over asphalt. What about multiple, close-together landings? Will hot asphalt debris stay off the fighter’s stealthy skin?

Nobody seems willing to say when such tests will be conducted—which is odd, because we do flight tests to prove the airplane can meet requirements. How was the requirement for the F-35B to VL on a non-standard runway framed? Indeed, was that requirement formally defined at all? Omitting the latter would have been a catastrophic mistake by the Pentagon.

At least $21 billion out of of the JSF’s $55 billion research and development bill is directly attributable to the F-35B variant, which also has the highest unit cost of any military aircraft in production. The design compromises in the F-35B have added weight, drag and cost to the F-35A and F-35C. It would be nice to know that—air shows aside—it will deliver some of its promised operational utility.