P-51, F-16, F-15 and F-22 (World Fighter Aircraft Collection)

Three generations of American fighter aircraft in formation at the 2006 "Aviation Nation" airshow at Nellis AFB near Las Vegas.

The F-16 Fighting Falcon and F-15 Eagle in the photo are usually classified as "fourth generation" fighters, while the F-22 Raptor is the only operational "fifth generation" fighter.   However the boundary lines between generations is very imprecise, and some aircraft like the Gripen, MiG-35, Sukhoi Su-30 and F-18 Super Hornet are even said rather ungrammatically to be "fourth and a half generation aircraft", sometimes abbreviated to 4.5th generation.

The reality is that almost for a century fighter aircraft technology has advanced faster than almost any other branch of technology, and has incorporated other new technologies as soon as they became practical, including radio, radar, rocket power, cathode ray tubes, transistors, micro-electronics, lasers and GPS, to name just a few.   Indeed if you say that the first world war one fighters were "generation one", then already by the end of that war several generations of fighters had come and gone, because aircraft in service at the start of the war were completely out-classed by the aircraft in use at the end.   Development slowed between the two world wars, but in the lead-up to the second world war biplane fighters became obsolete as faster monoplane designs came into service.   The war saw the development of the first jet fighters, and though the very first, the Me262 Schwalbe, had swept wings, the early British and American jets like the Meteor, Vampire, Venom and Shooting Star all had straight wings and could therefore be considered "first generation" jet fighters.  Technology advanced during the Korean war with next generation swept-wing fighters like the MiG-15 "Fagot" and F-86 Sabre, then settled into a steady pattern of progress as the cold war developed, with supersonic fighters like the MiG-21 "Fishbed" and F-104 Starfighter.   The Vietnam era saw the development and introduction of aircraft like the F-4 Phantom II and the F-14 Tomcat, and then aircraft like the MiG-29 "Fulcrum", Su-27 "Flanker", F-15 Eagle and F-16 Fighting Falcon, which defined the final part of the cold war.

Although a new generation of fighters is coming into service now, aircraft like the Eurofighter Typhoon, Dassault Rafale, Gripen, F-22 Raptor and F-35 Lightning II, the future has never looked less interesting for fighter aircraft enthusiasts, with aircraft development taking longer and longer, military budgets getting smaller and the possibility of unmanned combat air vehicles (UCAVs) taking pilots out of the picture entirely.