Not unlike the F-35, this high-tech, high-speed, high-stealth jet comes with a major price tag. Here's What You Need to Remember: The biggest downside of the Su-57 has been its cost, and Russia has been slow to receive the aircraft. Codenamed the "Felon" by NATO, Russia's Su-57 stealth fighter has the potential to be a dangerous adversary in the sky as it combines stealth and speed with advanced weapons and state-of-the-art sensors. Su-57 Stealth Fighter: Why the 'Felon' Is So Dangerous Developed by Sukhoi Design Bureau and the Russian Aircraft Corporation as part of the Russian Air Force's PAK FA fifth-generation fighter jet program, the aircraft has been slower to arrive than Moscow may have initially planned. However, the Su-57 will eventually replace the Russian military's MiG-29 and Su-27 fourth-generation aircraft.