Keeping 4th-Gen Fighters in the Game

Oct. 1, 2019

An F-16 releases a flare in the USAF CENTCOM area of responsibility. F-16s have had countless capability upgrades, patches, and life-extension mods since joining the fleet in the 1980s and early 1990s. Photo: SSgt. Chris Drzazgowski

The Air Force planned for a fighter force comprised mostly of stealthy, networked, and hyper-situationally aware F-22 and F-35 fighters. But the premature termination of the F-22, delays with the F-35, and decades of anemic investment mean USAF will have to rely on its 1980s-era fourth-generation jets for many years to come.

To keep its A-10s, F-15s, and F-16s combat-relevant and capable, the Air Force is strengthening their fatigued structures and buying avionics that will let them get close to the battle. To strike deep, USAF is buying stealthy standoff missiles to keep them in the game.

“Fourth generation will be with us into the 2030s,” USAF Chief of Staff Gen. David L. Goldfein told Air Force Magazine in a recent interview. That’s a major challenge in executing the National Defense Strategy, because the fighter fleet “is the oldest it’s ever been,” on average, while competitor air defenses continue to improve, and adversary air fleets bulge with new airframes.

Even adding 48 or 60 new F-35s per year doesn‘t chip away much at the 28-year average age of the fighter fleet. To bring that number down to something manageable, the service needs to buy 72 new airframes annually, and the F-35 production line hasn’t spun up to that level yet.

“At 48, 72, or even 100” new fighters a year, “we’re going to have a mix of fourth- and fifth-gen for a long time,” said Air Combat Command chief Gen. James M. Holmes in August. “I think that was always a reality.”

Click here or on the image above to view Air Force Magazine’s infographic as a full-size PDF. Teaser graphic: Dashton Parham/staff.

The ratio of 4th-to-5th-gen aircraft in the fighter force is 82 percent to 18 percent, said retired USAF Lt. Gen. David A. Deptula, dean of AFA’s Mitchell Institute for Aerospace Studies. “Not all contingencies will require fifth-generation capability,” he added. “Fourth generation will suffice in relatively permissive airspace.” But, “the Air Force needs to maintain air superiority across the spectrum of conflict.”

At Air Force Materiel Command’s Life Cycle Industry Days in June, Brig. Gen. Heath A. Collins, program executive officer for fighters and bombers, said the Air Force is investing in an expansive program of aircraft modifications for its existing fighters. He said in the year leading up to his presentation, 221 modifications were performed on the A-10; 970 on F-15s; and 281 on F-16s. To accelerate the improvement of older fighters, Collins said AFMC is trying to integrate new information technologies and tools, upgrade its facilities, and hire new talent as rapidly as possible.

The four fourth-gen fighters are collectively getting $15.9 billion worth of new investment over the next five years, not including regular repair and maintenance or the purchase of new F-15EXs included in the 2020 budget.

“And so, what do you do to keep those [fourth-gen] airplanes relevant and useful” Holmes said. “We have plans.”

Contractor Dale Benoit inspects paint beneath a new A-10 Thunderbolt wing at Hill AFB, Utah. The aircraft was the last of 173 to receive new wings under the initial program, which extends the life of the fleet. Photo: Alex Lloyd/USAF


From 2018 to 2024, the Air Force plans to spend nearly $2.9 billion on a life-extension program for the A-10C Thunderbolt II. The last update gave the “Warthog” a digital backbone, a helmet-mounted cueing system, and the ability to carry multiple new Global Positioning System-enabled precision weapons.

Boeing completed the first phase of rewinging the A-10 in August, providing new wings for 173 aircraft, adding 10,000 flight hours—or about 10 years—to their service lives. That means the jets can fly safely well into the 2030s. The upgrade also installed a new wire-bundling arrangement to make the wings easier to remove, service, or modify. Boeing received a follow-on contract worth up to $1.3 billion in August that could replace the wings on 109 remaining aircraft, plus a few spare sets, under the Thunderbolt Advanced-Wing Continuation Kit, or ATTACK.

“We’re focused on the re-winging effort to make them structurally sound,” Holmes said of the A-10. Other A-10 upgrades underway include the Lightweight Airborne Recovery System, which is a radio system to make it easier for A-10 pilots to find downed airmen in hostile territory and protect them until they can be extracted; a new Identification, Friend, or Foe system; a new On-Board Oxygen Generating System; new computer software, radios, and a high-resolution display; and anti-jam Global Positioning System capability. A new computer could also be in the offing.

The A-10 will also get a raft of new weapons, including the Small Diameter Bomb, a new variant of the Joint Direct Attack Munition; a new laser-guided rocket; and the AIM-9X dogfight weapon for self-defense. The requested funds also buy contract depot maintenance in the Pacific Theater and fuselage repairs.

An F-15 (left, rear) flies in formation with two F-22s over Nevada. USAF is buying new-build F-15EXs. At least 80 are expected to be produced. Photo: SSgt. Daryn Murphy


The F-15’s life expectancy has been much in the news in the last year because the Air Force was presented with a plan by the Office of the Secretary of Defense to buy brand-new air superiority versions of the airplane, known as F-15EX, that the service didn‘t ask for. Congress funded eight airplanes in the fiscal year 2020 budget. At least 80—and as many as 144—aircraft could be built.

Why buy “new old” airplanes? The F-15C and D models “won’t make it” to the late 2020s, Air Force Materiel Command chief Gen. Arnold M. Bunch Jr. told Air Force Magazine in an interview. The aircraft now in the fleet are speed- and load-limited due to stress fatigue in key parts, such as the longerons, Bunch noted. Longerons are major load-bearing structures running alongside the cockpit and connecting the front of the aircraft to the back; they were “life of the aircraft” parts specified to last up to 30 years. The F-15Cs and Ds have exceeded the parts’ life expectancy and replacing them entails virtually dismantling the aircraft.

Goldfein said the Air Force agreed to OSD’s plan to buy new Eagles because the service needs more fighters, and Lockheed Martin can’t boost production to the required 72 F-35s per year fast enough. The F-15EX will rapidly slide into existing squadrons, Boeing argues, using existing ground equipment and weapons, and pilots will transition to the new version in only a few months.

A similar version of the F-15 are in production for the United Arab Emirates, and it is that version that’s the basis for the F-15EX. Development costs have been amortized and testing is nearly complete on foreign variants, so those costs can be saved, the Air Force asserted.

On the jets that it will retain—of both the air superiority F-15C/D and E model for strike—the Air Force has budgeted $7.6 billion for hardware upgrades and life-extension modifications for the period 2018 to 2023.

The biggest capability upgrade planned for F-15s is the Eagle Passive/Active Warning Survivability System, or EPAWSS. This electronic warfare system should provide a big increase in the jet’s situational awareness, its ability to autonomously and automatically detect threats, jam enemy radars, geolocate enemy emitters, defeat enemy electro-optical and infrared sensors, and function in a “highly contested” battle space, according to Boeing and the Air Force.

EPAWSS will also manage the F-15’s deployment of physical countermeasures, such as chaff. The EPAWSS is estimated to be a $2.4 billion program in then-year dollars, and it goes beyond the future years defense plan.

“EPAWSS is the answer, we think, for the F-15 fleet,” Holmes asserted. He also noted that an effort to re-equip the F-15 inventory with Active Electronically Scanned Array (AESA) radars has been “really successful” and is “fairly close to being complete.”

Boeing officials, at an advance Paris Air Show briefing earlier this year, said the EPAWSS will “buy back” some of the Eagle’s ability to approach modern adversary air defenses.

The EPAWSS was put on hold for a couple of years as the Air Force wrestled with how long it would keep the F-15, and a Pentagon inspector general report at the time said the funding was diverted to an unnamed “higher priority” air superiority program.

The Pentagon’s Selected Acquisition Reports for 2018, released in July, describe major program cost and schedule fluctuations. The Defense Department said EPAWSS had experienced a cost increase of 24.3 percent because of a sharp reduction in the number of units the Air Force programmed. The program will be revisited later this year by the Defense Acquisition Board, which will determine if it is mature enough to move forward.

“Like most complex programs,” Holmes said in April, the EPAWSS suffered from a combination of inconsistent funding and shifting requirements. The system “won’t make an F-15 into an F-35 or an F-22, but it makes it a whole lot better, and it expands the envelope quite a bit,” he said. “I’m in favor of continuing the investment.” Initially, Holmes said, installing EPAWSS will reduce F-15 availability, but “we have a plan to do it, and we’ll manage it.”

Collins reported that the EPAWSS is actually moving about a year faster than it normally would because one of his program managers had the idea—employing new authorities from Congress—to “break up the program” into “multiple decision points,” with fewer reviews looking at more manageable chunks.

The EPAWSS upgrade goes hand in hand with a new processor for the Eagle, which will give the F-15 the fastest fighter processor flying. Other major initiatives include a new Infrared Search and Track system, to assist the F-15 in seeing, tracking, and shooting stealthier targets; the MIDS/JTRS (Multifunctional Information Distribution System/Joint Tactical Radio System) digital data link and programmable radio; and a new cockpit pressure monitor and warning system.

Future F-15 improvements under consideration include a full cockpit upgrade with new displays; a ground collision warning system; “3-D” audio; a pod to allow direct, encrypted and low probability of intercept communications with fifth-gen aircraft; removable memory; and a Digital Radio Frequency Memory (DRFM) pod. In very basic terms, a DRFM can capture an incoming radar signal and send it back, attenuating its own signature, and fooling the radar into thinking the aircraft is somewhere else, or is a different kind of aircraft.


The most numerous of the Air Force’s fighters, the F-16 has had countless capability upgrades, patches, bulkhead strengtheners, and life-extension modifications since joining the fleet at a rate of hundreds per year in the 1980s and early 1990s.

The Air Force has planned to spend $5.4 billion on F-16 upgrades from 2018 to 2023, with the biggest improvement being an AESA radar, which will become operational on some jets this year and will be fully equipped across the Falcon fleet by fiscal 2025. In addition, a service life extension program intended to add up to 8,000 hours to the F-16’s service life is planned to begin around fiscal 2022, with completion in fiscal 2029.

The F-16’s Auto Ground Collision Avoidance System, or Auto-GCAS, has already been installed in some aircraft and should be widely in place in two years, with the whole fleet equipped by fiscal 2025. A modular mission computer is also in final development and should start installations next year.

Further improvements include a new digital radar warning receiver, a new operational flight program, the MIDS/JTRS and a communication suite upgrade, all planned for initial capability in the early 2020s and full fleetwide installation by the late 2020s.

The Air Force is also pursuing integration of the B61-12 tactical nuclear weapon on the F-16, as well as the Advanced Precision Kill Weapon System, which is a new precision seeker warhead for the Hydra rocket.

The radar and digital radar warning receiver upgrades are to ensure that the F-16 “can detect the more modern threats,” while the new computer will “tie those things together,” Holmes said in August.


Across the fourth-gen fleet, Holmes said the Air Force is considering “options for a next-generation jamming pod.” He said USAF has worked with contractors and is “evaluating that, and we hope to make some decisions” in time for the 2021 Program Objective Memorandum.

He acknowledged that the Air Force has invested heavily in refilling its weapons stocks, saying “we’ve made good progress in trying to buy back depleted munitions” used heavily in the “15 years of a pretty kinetic operation in Afghanistan and Iraq.” Because of the need to limit collateral damage, the vast majority of weapons used were what are called “preferred” munitions, which Holmes described as the Joint Direct Attack Munition, Small Diameter Bomb, and Hellfire missile.

The Air Force also recently revealed that it has sharply increased its planned acquisition of the AGM-158 Joint Air-to-Surface Standoff Missile (JASSM), a long-range, stealthy weapon that can be launched by a nonstealthy, fourth-gen aircraft from well outside enemy air defenses. The Air Force will nearly double its planned acquisition from 4,000 units to more than 7,200. Production will shift to the longest-ranged variant, the AGM-158D.

Asked if USAF was trying to accomplish with stealthy missiles what it can’t manage by buying stealthy aircraft, Holmes would only say that the JASSM is “a fairly important capability” useful for “deterring peer adversaries.”

He also said he doesn’t anticipate a time when USAF won’t need to be able to penetrate enemy air defenses. Adversaries—noting what USAF is “good at”—are investing in mobile air defenses, anti-satellite systems, and theater ballistic missiles. Attacking these targets requires either “exquisite knowledge” of their movements or a platform operating “in and around them,” Holmes said. “Those are the kind of trade-offs we look at.”

And for those missions that the fourth-gen force can’t take on, the fifth-gen airplanes will be available, Holmes said. “There will still be places they can’t go and things they can’t do, that the fifth-gen airplanes can.”