Categorization of fighter jets in generations is a classification system used around the world. The basic classification into five generations is widely accepted and recognized. Some accounts have subdivided the 4th generation into 4 and 4.5, or 4+ and 4++.
Sixth generation Fighter Aircraft
With the fifth generation slowly coming into service, attention is already turning to a replacement sixth generation. The requirements for such a fighter are already under debate in the drawing board stage. The fifth-generation abilities for battlefield survivability, air superiority and ground support will need to be enhanced and adapted to the future threat environment.
Development time and cost are likely to prove major factors in laying out practical roadmaps for 6th generation aircraft. These aircraft may not be available for decades.
These aircraft could have features like hypersonic speed, dual-mode engines, and adaptive shapes.
At this stage it is not clear as to what extent drones and other remote unmanned technologies will be able to participate, either as satellite aircraft under a sixth generation command fighter, or even replacing the pilot in an autonomous or semi-autonomous command aircraft.
Studies such as the US F/A-XX program and UK-led BAE Systems Tempest are ongoing. Projects related to unmanned combat aircraft systems are in progress, such as the joint French- Swedish nEUROn, the UK’s BAE Taranis, Northrop Grumman’s X-47B and the US Navy’s follow-on UCLASS program. Similar unmanned combat aircraft projects are also underway in Russia and China.
References:
https://www.airforce-technology.com/features/top-sixth-generation-fighter-jets/
https://www.sldinfo.com/wp-content/uploads/2014/05/Air-Combat-Seminar-summary-AndrewMcL.pdf
https://www.fighterworld.com.au/az-of-fighter-aircraft/five-generations-of-jets
http://www.codeonemagazine.com/archives/2005/articles/oct_05/
https://en.wikipedia.org/wiki/Fifth_generation_fighter
https://migflug.com/jetflights/fighter-jet-generations/
http://www.aerospaceweb.org/question/history/q0182.shtml
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