Shuttle Discovery

               Development of two fighters in parallel with complementary roles, one heavyweight and more costly and the other light and relatively cheap, is far from unprecedented. The F-22 as an elite heavy fighter built to engage the most advanced enemy combat aircraft is a direct successor to the F-15C Eagle and F-4E Phantom from the respective fourth and third generations, while the F-35 follows on from the F-16 Falcon and the F-5E Tiger II in fulfilling the role of a low cost and versatile light fighter capable of fulfilling any number of roles on the battlefield but specialised in none of them. The heavy air superiority fighters have been far more restricted in their exports compared to their lighter counterparts, with the F-22 banned from export entirely while lighter aircraft have been built in much larger numbers, widely exported to all manner of U.S. allies and non aligned states, and in the fourth and fifth generations also acquired in much larger numbers by the U.S. Milita