What does ‘generation’ mean in the context of fighter jets?

Sub : Sci

Sec: Defence

Context:

Unverified images of what is being termed as a Chinese sixth generation fighter aircraft, named the J-36, have gone viral on social media.

What does ‘generation’ mean:

The concept of “aircraft generations” emerged in the 1990s and applies mainly to fighter jets. Each generation marks a significant leap in fighter jet technology.
There’s no strict definition of what constitutes a generation and these generations serve as a general guideline to compare aircraft technology, not a precise measure of their capabilities.
Generational shifts typically occur when new technological innovations are too significant to be integrated into existing designs through upgrades.
There are currently five generations of fighter jets which are (or were in the past) in active service, with sixth generation jets currently in development.

First Generation (1943 to 1955):

The first generation of fighter jets emerged during the final years of World War II.
Early jet fighters, faster than piston-engine fighters but still subsonic.
Basic avionics, no self-protection systems, and armed with machine guns or cannons.
These aircraft were deployed as interceptors, and could engage in combat within close visual range.
Examples: Messerschmitt Me 262, Mikoyan-Gurevich MiG-15.

Second Generation (1955-1970):

Introduction of afterburners and swept wings allowed second-generation aircraft to achieve transonic and supersonic speeds in level flight.
Fire control radars were introduced, along with the first semi-active radar-guided missiles.
Radar warning receivers were added, paving the way for countermeasure systems.
Examples: MiG-21, Lockheed F-104 Starfighter.

Third Generation (1960 to 1970):

Integrated designs, multi-role capabilities (fighter-bombers and interceptors), beyond-visual-range combat, pulse-doppler radar, and electronic warfare systems.
Aircraft featured more powerful turbofan engines for superior range, manoeuvrability, and sustained supersonic flight.
Examples: McDonnell Douglas F-4 Phantom, MiG-23, Hawker Siddeley Harrier.

Fourth Generation (1970-2000s):

Fly-by-Wire (FBW) Technology: The introduction of FBW systems allowed for greater manoeuvrability and more stable flight at high speeds by using computers to mediate between the pilot’s input and the aircraft’s control surfaces.
The introduction of advanced avionics, including heads-up displays (HUDs) and improved electronic warfare systems.
Stealth (ability to be invisible to radar systems) designs: Composite construction materials, radar absorbent paints etc.
Examples: F-16 Fighting Falcon, Sukhoi Su-30, Dassault Rafale.

Fifth Generation (2000s-present):

Fifth-generation fighter jets are the most advanced aircraft in operation today. They feature stealth technology, integrated systems that give pilots a full view of the battlefield, and networked communication that allows them to act as a coordinated team.
Advanced computer systems help automate many functions, reducing pilot workload and increasing operational effectiveness.
The Lockheed Martin F-22 Raptor, introduced in 2005, was the first of its kind. It remains unmatched in stealth and long-range combat, with a radar signature as small as a bird’s and advanced systems to detect and eliminate enemies before being detected.
Currently, only the US (F-22, F-35), Russia (Sukhoi Su-57), and China (Chengdu J-20) operate fifth-generation fighters.
India is developing its own but is still far from building a prototype.

Sixth Generation (in development):

Speculated Features: May include optionally-manned or unmanned capabilities, hypersonic speeds, advanced AI, directed-energy weapons (e.g., lasers), and possibly suborbital flight.
Potential Examples: Tempest (UK, Italy, Japan), FCAS (Future Combat Air System) (France, Germany, Spain)