The U.S. Air Force Has a Master Plan for the F-15EX Fighter The Air Force has estimated F-15EX fighter shares about 70 percent of parts with the current F-15Cs and F-15Es that they will be replacing. Not only are the original production lines in St. Louis still in place, but the training facilities, maintenance depots, and other infrastructure can be also be readily shifted to F-15EX support. Even as the United States Air Force continues to acquire the fifth-generation Lockheed Martin F-35 Lightning II fighter jet, the service will also be receiving the latest updated version of the Boeing F-15 – a platform that first took flight long before many of today's pilots were even born. However, the F-15EX is far more advanced than the original F-15A that was introduced in 1974 and entered service two years later.