In the mid-1980s, the missing “F-19” designation helped fuel rumors of a secret American stealth fighter, amplified by a highly plausible model kit that went viral and even drew attention in Congress.

Stealth — or low-observable – technology used to be rare on aircraft, only seen on the F-117 Nighthawk and B-2 Spirit, but it's the defining feature of an entire generation of fighter jets like the ...