via Wikimedia Commons Boeing Co. is pitching a new version of the F-15 Eagle as the service defines its inventory mix of fourth- and fifth-generation aircraft. Known as F-15X, the fighter would be equipped with better avionics and radars and would carry more than two dozen air-to-air missiles. The move comes as officials in recent months have considered retiring the older F-15C/D fleet. There may be a new-old fighter jet on the horizon for the U.S.