Why do European countries, Russia and the US consider the generations of aircraft different?
Here's how SAAB separate the generations.
1st generation Includes early jet driven warplanes, such as the Vampire, MiG-15, F-86 and the J29.
2nd generation are jet fighter aircraft were weapons integration and avionic systems was being introduced. This generation involves the MiG-21, F-5 Freedom Fighter, F-4 Phantom, 32 Lansen and J35 Draken
3rd generation are supersonic fighter aircraft with an infrastructure based on separate digital systems, who takes great advantage of computers to achieve functionality. Aircrafts included in this generation are for example the MiG-29, Su-27, F-15, F-16, F-18, Mirage 2000 and the Viggen.
4th generation are supersonic aircrafts with a digitally constructed infrastructure, with fully integrated computerized systems, which uses a common computerbase with a standardized interface. This means that sensors, weapons, control surfaces, control organs, displays and so on can be used as information suppliers and information carriers; offering in theory an infinite number of combinations in which to create the systemfunctions desired. The only limit are the laws of physics and the human being. Included in this generation are, the F-22, F-35, the Rafale, the Eurofighter and the Gripen. The principle structure creates a very high development potential, and has the ability to fully take advantage of future advancements in sensors, weapons and computers and so on. The 4th gen fighter remains young over time. New system functions can be created when there is a need for it, depending on the tactical demands, and the technical development.
That is typical examples for the differences in the definition of jet fighter generations in Europe and the US/Russia.
In Europe aircraft like the F-16 or MiG-29 are classed as 3rd generation, while the same aircraft are classed a 4th generation in the US/Russia. Therefore their successors must belong to the 4th generation in Europe, but 5th generation in the US/Russia. That is the reason why Europeans refer the 4th generation to aircraft like Gripen, Rafale or Eurofighter. That means a European 4th is a US 5th!!!
The USA considers the only 2 5th Generation fighters to be typically American made F-22 and -35. Marketing tool? Confuses me..