The Air Force's new "Penetrating Counter Air" fighter jet won't replace F-22 Raptors in the skies until sometime in the 2030s, but the Air Force is already finalizing technology requirements for the plane, according to Popular Mechanics.

The sixth-generation fighter will take on entirely new foes current Raptors can't, like Russian weapons such as the S-400 air defense missile system and the Su-57 fighter. Air Combat Commander General Mike Holmes said F-22s and F-35s are continually upgraded, but it's time for an overhaul.

This is the first time the U.S. will design a clean-sheet fighter in 20 years. The PCA will emphasize range to better escort B-2 and B-21 bombers over Russia and the Asia Pacific region. It will also lose the vertical tail fins that are standard on many military planes so it can be stealthier.

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The Air Force requested $294.7 million in fiscal 2018 for continued PCA technology studies and funding to nail down specifications for the new fighter jet.

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