>Fifth generation fighters differ from their fourth generation predecessors in a number of respects. The three main initial criteria were the ability to fly supersonically for sustained periods without using afterburners, known as a supercruise capability, as well as using a very low observable stealth airframe and having enhanced manoeuvrability. While the F-22 meets all three, however, the cheaper F-35 has neither supercruise nor high manoeuvrability. So, not actually 5th gen.