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. F-35 is on track to become by far the military’s most numerous warplane. It was designed to replace almost all current fighters in the Air Force and Marine Corps and complement the Navy’s existing F/A-18s.