Image 1: Lockheed F-22A Raptor, the first and only 5th generation fighter currently in service world wide.
With the emergence of new 5th generation stealth fighter designs from around the world, some have concluded that 4th generation fighters will cease to be relevant to future conflicts. This is simply not the case; fourth generation aircraft will remain in wide spread use by air forces world wide for another two decades. The last 4th generation aircraft will likely not be fully retired until around three decades from now. Third generation fighters such as the F-4 Phantom continued to serve long after the emergence of the 4th generation series of fighters like the F-15. Japan recently secured a deal, the F-X program, to replace its reconnaissance variant F-4 phantoms with the F-35. Likewise, upgraded derivatives of fourth generation aircraft will continue to be utilized because of procurement issues, budgetary concerns, and desired capability to equipment based decision making on behalf of governments. Following this explanation, the future of 4th generation aircraft in the USAF, Indian Air Force, Russian Air Force and Chinese Air Force will be discussed.
A generation of aircraft is defined by both the historical period in which was developed in addition to its general technological and design characteristics. With each progressing generation of fighter aircraft, the difficulty and cost to produce the new generation of aircraft rises significantly. (See Rising Fighter Aircraft Costs Over Time: http://manglermuldoon.blogspot.com/2011/07/usaf-fighter-aircraft-cost-over-time.html). For this reason, it is impractical to acquire large numbers of a new generation of aircraft very quickly. When initial production of the F-15 began, it was an extremely expensive aircraft relative to its predecessor. Adjusted for inflation, the F-15 costs roughly three times as much as the F-4 (38.6 million vs. 13.6 million 2011 USD). Likewise, the F-22 Raptor costs roughly four times as much as the F-15. Over time, costs lower and production becomes cheaper. Furthermore, the complexity of modern fighter aircraft ensures that their deployment will be phased and take years. The days of quick mass production and immediate entry into service (e.g. World War II) is over. The USAF's full order of F-15A's was delivered to the USAF over the course of seven years. During that time, the proceeding aircraft is gradually phased out. Today, the older F-15's and F-16's that are not chosen for upgrades are being phased out in preparation for the USAF's transition to the F-35.
From a budgetary standpoint, most nations have opted to upgrade their existing 4th generation aircraft as opposed to seeking a new 5th generation aircraft. The cost is simply to high at this point for many nations to procure the 150 million dollar F-35 in large numbers (price variable if developmental costs included and by variant some estimates higher than 200 million). Both the funds and technology required to build 5th generation aircraft ensures the use of upgraded 4th generation jets. Only the United States, China, Russia, and India have stealth programs that have or will come to fruition within the next decade. The state of Japan's military industrial complex is such that domestic production of the proposed ADT-X would be intolerably high.
More info: http://thediplomat.com/2011/06/23/japan%E2%80%99s-stealth-fighter-gambit/?all=true
Another reason why 4th generation aircraft will persist is many governments have decided that they do not need the stealth capability that 5th generation aircraft provide. Arguably the most intelligent method of procuring equipment is a capability to equipment based approach. That is, a government determines what capability it needs to ensure its own national security. Upon deciding what capability(s) is needed, the government looks for equipment to best enforce the desired capability. Furthermore, many governments have put less importance on defense especially within Europe. Limited budgets and high personnel expenditures means even fewer funds can be allocated to equipment procurement.
Despite the recent media attention to China's second stealth fighter program, China's air force will largely be predominately composed 4th generation fighters with 3rd generation fighters being phased out over the next decade. The J-10, Su-30, Su-27, J-11, and J-15 will continue to serve past 2020 in China's air force and navy. The J-20 will likely begin to enter service around 2017-2018. However, after 2020, China is capable and will likely produce hundreds of stealth aircraft. Based on the limited information the public has on the J-31, it will likely be produced in heavier numbers than the bulky J-20 as the J-31 fulfills the light fighter requirement role. Furthermore, China is the only power aside from the United States who can finance multiple stealth fighter programs on its own. The Chinese military budget is expected to grow by 142% between 2010-2015. (WSJ, 2011) Chinese pilot quality has also increased with the rapid increase of mandatory flight hours per year (100-200 hours REF 8) However, the quality and technological complexity of China's stealth fighters remains dubious compared to its U.S and Russian peers.
Despite the concern over the PAK FA, the majority of Russia's air force will be comprised of upgraded 4th generation fighters. Russia plans to spend 600 billion dollars over the next decade on weapon procurement. (Russian Today, 2010) The 4.5 generation Su-35S will be ordered in large numbers. Russia plans to procure 250 PAK FA fighters with the possibility of a second stealth fighter program, the Sukohi LMFS, being produced later on.
India recently announced with would reduce its PAK FA order to 144 down from the original 200 (India Strategic 2012) due to cost concerns. Although the MRCA program is currently in limbo, India's future air force composition will largely be comprised of 4th generation fighters regardless. The 3rd generation Mig 21 will likely be phased out over the coming decade. India recently finalized a deal upgrade its fleet of Su-30MKI fighters for 3 billion dollars. The 4th generation HAL Tejas and 4.5 Rafale (pending investigation) will serve in India's Air Force and Navy. The AMCA program might come to fruition (Domestically produced Indian 5th generation fighter) but it is not planned to enter service until past 2020.
Fourth generation aircraft will continue to operate world wide for at least the next three decades. The continued use of 4th generation aircraft does not indicate that 4th generation aircraft can evenly complete with 5th generation aircraft. If both pilots have similar training standards, the 5th generation pilot has a distinct advantage. When the F-15 was first deployed in Israel, the 3rd generation Syrian Migs were easily destroyed with no F-15 losses. Likewise, modern F-22A's participate in 1 vs. 4 to 5 engagements against F-15's and routinely win. Even a lower quality 5th generation fighter, such as the F-35, has the advantage over a 4.5 generation aircraft like the Su-30MKI. (Author's Note: If you vehemently disagree feel free to comment and I will debate with you provided you are not a troll)
Image 3: Lockheed Martin F-35. Image Credit: Flight Global. My evaluation of the F-35: http://manglermuldoon.blogspot.com/2012/05/f-35-development-and-performance.html