F-15 ACTIVE: This Frankenstein Fighter Was Better Than the F-15 Eagle NASA's ACTIVE program resulted in a Frankenstein fighter with a variety of components and systems that managed to make the legendary F-15 even better. The F-15 has long been a legendary fighter, but NASA’s ACTIVE program aimed to make it even better. Faced with the looming threat of nuclear war with the Soviet Union, the United States began testing next-generation capabilities before the 10th F-15 even rolled off the assembly line. In the 44 years since the F-15 Eagle first entered service, the air superiority fighter has proven its combat mettle time and time again, racking up an astonishing 104 kills against enemy fighters without ever losing a bout. Today, the twin-engined F-15 remains the fastest fighter in the American stable — with a top speed of Mach 2.5 that eclipses both its super-computing younger sisters, the F-22 and F-35.