Fighter F-15 EX

4th Gen Fighters : Relevance in current era

– Prasanth GS

As we all know, the 5th and 6th generation fighter programmes has been the hot topic for quite some time. All the world powers are pursuing 5th generation fighter programs and some have even made a direct leap into the 6th generation. The current 5th generation fighter jets in active service F-22 & F-35 from US, Su-57 from Russia, J-20 from China. Those under development are AMCA from India, KFX from South Korea, TFX from Turkey, J-31 from China and FX by Japan. The US, Russia, UK and France have already jumped into the 6th generation fighter development programmes. The US is going for Next Generation Air Dominance (NGAD). France, Germany & Spain are going for FCAS, UK for Tempest and Russia for MiG-41.

US needs 4th gen fighters

Despite the progress of these programmes, the USAF surprisingly has recently placed an order from Boeing for its first batch of 8 F-15EX fighter jets. This is a five minus generation fighter jet which was under development. This is when the US is actively pushing their 5th generation fighter aircraft F-35 within their service ,to its allies and NATO nations. The total value of the contract is around $26 Billion. We expect US to place orders for at least 144 fighters. Instead of investing to procure additional F-35s, they are going for the much-improved version of F-15 to quickly replace the aging squadrons of F-15 C/Ds.

F-15 EX

Additionally, the USAF is also pursuing a new light weight non-stealthy fighter jet programme to replace the large number of F-16s in their inventory. They are planning to design something that is a 5-minus generation with a mix of capabilities and systems from active 4th and 5th generation aircrafts inspired by Digital Engineering.



US had earlier developed T-7A Advanced Jet Trainer within a few years using the same Digital Engineering concept. It allows to reduce the development span by incorporating the proven systems from different platform. They have named the programme as F-36 Kingsnake. It will use F-22’s PW F-119 engine, AN/APG-83 advanced electronically scanned array radar from current F-16 Viper. It also will have internal weapons bay apart from the wing-mount hardpoints. The aircraft is expected to enter the active service before 2030. They are going for the same class of fighter as a replacement for the F-16s to keep the squadron numbers high.

These two 4.5 gen or 5-minus gen programmes from the world’s most powerful nation has raised a big question.

Why new 5-minus generation aircrafts when we have moved on to 5th and 6th generation ones? And why now?

Why 4 and 4+ generation fighters are in high demand in 5+ generation era?

It’s not just the US. India is also pursuing a 4+ generation fighter variants like Tejas MK1, Tejas MK1A, Tejas MK2 or MWF, TEDBF. France is going for an upgraded version of Rafale called F4 Standard over the F3 Standard. Sweden is going for the SAAB Gripen E. Other few nations are upgrading their aging F-16 to Viper or Block70/72 Standard. So before jumping into a conclusion and criticizing such approach from the forces around the world, let us understand why the 4th generation fighters are still relevant. We will take you through a simple comparison about the factors affecting 4th and 5th generation fighters. This will give you a better understanding.

4th Generation Fighters5th Generation Fighters
Low operational costVery high operational cost
High service availabilityLow service availability
Low maintenance costExtremely high maintenance cost
Affordable to forces around the worldNot affordable as it is too costly to buy and maintain
Similar MRO and training requirementsAdapting to new MRO
Conflicting information about situationWell fused avionics to give clear situational awareness
More weapon payloadLess weapon payload as the weapons are carried in the internal weapon bay to keep the stealth profile
Can be mass produced in considerable numbersLow production due to its over pricing
Sortie rate is high due to low service & maintenanceLow sortie rate due to high maintenance

What 5th gen fighters entail to

As we all know, the 5th generation fighters are designed to be stealthy by keeping a very low RCS profile. To maintain this low profile, it requires high level maintenance to its Radar Absorbent Coating (RAM) and airframe servicing. Due to this, the service availability of the 5th generation fighters are very less compared to the 4th generation fighters. These high-level maintenances contribute to the very high operational and maintenance cost which will be a nightmare for the forces if procured. Only very few countries can afford such super costly fighters. As the technology develops and when there is a leap in the generation, the complexity and the glitches also increase. The other biggest challenge is to adapt to the shift in the Maintenance, Repair & Overhaul (MRO) ecosystem of the 5th gen from 4th generation. If not properly organized, the entire squadrons could be grounded!


Moreover, there are only two 5th generation fighters in active service today, Lockheed Martin’s F-22 Raptor and F-35. And among them, F-35, the most expensive weapon system ever built is meddled with flaws and glitches. Airframe damage caused at supersonic speed, cabin pressure issues, logistic issue, visibility issue while landing and many others. The other stealth fighters near to active deployment are Russian Su-57 and Chinese J-20. They claim it to be completely stealthy though they don’t meet the benchmarks to be stealthy. Both have comparatively higher RCS to F-22 or F-35. The J-20 is meddled with low thrust engine and doesn’t have any thrust vectoring and super cruising without the afterburner. And none of the other stealth aircrafts under development have super cruising engines with TVC.

The problems of F-22

F-22 production is limited to 180 due to very high cost involved in production & MRO. Also, the concept of stealth is applicable only at beyond visual range. The so-called element of surprise of the stealth is blown the moment they launch their attack against their opponent. And if they fail to take down the opponent, in an aerial combat, these aircrafts cannot stay in beyond visual range for long and will have to engage in a dogfight within the visual range. Once they are in visual range, the angle of attack, maneuverability and man behind the machine decides the end game. Here, there is a high probability that these stealth fighters can be taken down even by a 3rd gen fighter.

F-22 raptor Fighter
F-22 Raptor

Game of Numbers as well

And next, the number matters! Many claim that only quality matters and suggest to focus on quality over quantity. As mentioned earlier, the stealth fighters cannot be produced in sheer numbers due to the costs involved unlike the 4th generation fighters. The number has its own advantage and that’s what China is doing. A swarm of 4th generation fighter can for sure saturate and take down the stealth fighters, with few loses. The dwelling number of 3rd and 4th generation aircrafts from the inventory can never be replaced with the same number of stealth fighters. So, the only option available is to develop a 5-minus generation aircraft or upgrade the 4th generation aircrafts to bring it to 4.5 or near 5th generation.

The Air Forces can operate a mix of 4/4+ and 5th generation fighters assigned for different roles to keep the squadron numbers high for long time. SEAD/DEAD and Combat Air Patrol can be assigned to the stealth fighters and the ground attack roles can be assigned to the 4th generation fighters as they can carry more payload. Also, when you consider the business aspect, the companies will keep these 4th generation platforms upgraded considering the export market as most of the nations can never afford to buy 5th generation fighter.

Challenges in upgrading the logistic chain, training the squadron, infrastructure modification to bases and its ecosystem to adopt the 5th gen fighters will keep the nations to still keep using and opt for 4th generation fighters.

How to keep the 4th gen fighters relevant?

The 4th generation fighters can be given a life extension at least for 3 to 4 decades by undergoing significant transformation. Some of these include improving the Radar Cross Section (RCS), Electronic Warfare, secure datalink, situational awareness, radar and incorporating many more systems which we will discuss further.

  • Upgrading with latest GaAs or GaN AESA Radars
  • Full open architecture digital glass cockpit display
  • Helmet Mounted Cueing System
  • Precision stand-off guided weapon package
  • Bringing structural upgrades
  • Incorporating Conformal Fuel Tank on the fuselage that opens up additional weapon stations.
  • Engine upgrade with higher thrust and efficiency with low infrared signature
  • Improving the survivability of the aircraft with new Identification Friend or Foe (IFF), Onboard Oxygen Generation System, Aircraft Automatic Recovery System, Passive or Active Sensor Suite with sensor fusion for better situational awareness, IRST and jamming pods.
  • Using Enclosed Weapon Pods (EWP) to reduce the cross section of the aircraft.
  • Teaming the aircrafts with unmanned UCAV “Loyal Wingman” using Man Machine Interface.
  • Using Secure datalink or Software Defined Radio for secure communication.
  • Fly-by-wire system
  • Improving the surveillance capabilities by using latest Electro Optical targeting systems.

Incorporating the above modifications can bring the existing 4th generation fighters to 4.5 or close to 5th generation capabilities.


LCA Tejas

Recently, some Defense Analysts criticized the HAL Tejas programme for its late induction and the time span taken to develop it. They also criticize about the relevance of a light weight fighter in this era with only about 60% indigenous contents. This comes when the HAL is going ahead with orders of MK1 & MK1A from the IAF and the development of future variants like MK2/MWF and TEDBF. HAL is also pursuing an autonomous programme for future aerial warfare called as CATS – Combat Air Teaming System . They showcased this during the Aero Indian 2021.

Here, a group of autonomous systems team up with a mother ship called LCA MAX as a “Loyal Wingman”.

Possible Upgradable Platforms:

  • F-15 C/D to F-15EX

F-15EX will come with new mission computer, ability to fire hypersonic weapons, more weapon payload (22 air to air missiles), digital fly-by-wire system, advanced electronic warfare, affordable life cycle cost. F-15EX also comes with a directed energy (laser) based self defence system to protect it from incoming missiles.

  • F-16 to F-16 Viper/Block 72

There are around 25 nations that operate different variants of F-16 Falcons. Recently, some of these counties have been trying to strike deal with Lockheed Martin to upgrade their current squadrons to Viper Standard also called as Block70/72.  

F-16 Block 70/72
  • Su-30 MKI to Super Su-30 MKI

The Super Sukhoi upgrade has been on talk for quite some time. Under the Su Su programme, IAF is trying to indigenize as many systems as possible. The expected upgrades to Su-30 MKI are its radar, cockpit and its avionic system and the Electronic Warfare suite.

Su-30 MKI
Su-30 MKI

Click here to read more about Super Sukhoi and watch about the upgrade programme at

So, there is some life left in the cost effective 4th gen fighters for at least the coming 3 to 4 decades. This is because most of the air forces around the world are trying to keep up with the future warfare through upgrades given their constrained funding.

By Alpha Defense

Alpha Defense initially a solo venture but now a defense group by people from various demographics of India covering defense news and updates. We believe in unbiased analysis of every subject in hand. Our mission is to provide simplfiied defense information to the public.

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