A F-35 Lightning II Joint Strike Fighter is seen at the Naval Air Station (NAS) Patuxent River

Americans should be worried.

The U.S. military has grounded all its new F-35 Joint Strike Fighters following an incident on June 23, when one of the high-tech warplanes caught fire on the runway of a Florida air base. The no-fly order — which affects at least 50 F-35s at training and test bases in Florida, Arizona, California and Maryland — began on the evening of July 3 and continued through July 11.

All those F-35s sitting idle could be a preview of a future in which potentially thousands of the Pentagon’s warplanes can’t reliably fly.

Handout photo of three F-35 Joint Strike Fighters flying over Edwards Air Force BaseTo be fair, the Pentagon routinely grounds warplanes on a temporary basis following accidents and malfunctions to buy investigators time to identify problems and to give engineers time to fix them.

But there’s real reason to worry. The June incident might reflect serious design flaws that could render the F-35 unsuitable for combat.

For starters, the Lockheed Martin-built F-35 — which can avoid sensor detection thanks to its special shape and coating — simply doesn’t work very well. The Pentagon has had to temporarily ground F-35s no fewer than 13 times since 2007, mostly due to problems with the plane’s Pratt & Whitney-made F135 engine, in particular, with the engines’ turbine blades. The stand-downs lasted at most a few weeks.