The term ‘generations’ applies to only jets rather than propeller driven fighter aircraft. During the 2000s Aerospace companies have also preferred to use generation-based categorization in order to differentiate between ‘old’ and ‘new’, fighter jet designs and capabilities and in a short time the notion of aircraft generations has turned into a marketing terminology. Lockheed Martin, for example, has labelled the F-35 Joint Strike Fighter a “fifth-generation” fighter in 2005, a term it borrowed from Russia in 2004 to describe the F-22. As a powerful marketing tool, the term ‘fifth-generation’ has been applied to the F-22 and F-35 aircraft, to underline that competing companies could not offer similar levels of performance and technological capabilities.  

However, even the ‘generations’ are supposed to be defined by new game-changing capabilities, since the evolving combat capabilities and requirements blur generational lines there is no clearly defined line between successive generations. Generational shift in fighter jets occurs when a technological innovation cannot be incorporated into an existing aircraft generation through upgrades and retrofits. Among the generational lines focus is shifting from platform to system-of-systems and each generation represents certain class of technology used in the fighter jet such as avionics, software, construction materials, network capability, engines, etc. A higher generation means a more technologically advanced platform.