F-15EX and F-35A? Allies Can Expand the Solution Set


Will the U.S. Air Force have what it takes to win the air-to-air fight with China or Russia? The answer isn’t so simple. Both countries continue to develop and field advanced fighters and area defense systems, but the challenges they pose are slightly different. China has improved its defenses, but its offensive ballistic and cruise missiles would force the Air Force to operate from a distance. A conflict with Russia, on the other hand, would entail greater air-to-air activity, placing a premium on the Air Force’s ability to quickly employ the most advanced fighters with a sufficient number of weapons. If an air-to-air fight with Russia is not won quickly, it would limit deployment of allied air, land, and naval forces and leave NATO forces vulnerable to attack.

Given recent developments in Beijing and Moscow — robust military modernization efforts combined with deepening political authoritarianism — the U.S. Air Force is concerned. While not specifically referencing either, the Air Force Air Superiority 2030 Flight Plan of May 2016 stated, “The Air Force’s projected force structure in 2030 is not capable of fighting and winning against this array of potential adversary capabilities.” This potential capability gap fuels a spirited discussion among those most interested in Air Force air-to-air capabilities. Two options have taken center stage: increasing the procurement of F-35 fighters or acquiring a new F-15 version, the EX, to augment the F-35 fleet.



The good news is that in any conceivable scenario, America would not have to fight China or Russia alone. Too often, this discussion around air-to-air confrontation with Russia and China doesn’t take into account the capabilities of our allies. As the Air Force’s F-15 fleet ages out, the Pentagon should encourage allies and partners to fill the gap. This would relieve pressure on the Air Force, improve interoperability, and strengthen deterrence. This option — which has not been given sufficient consideration — leverages America’s network of alliances to advance its interests.

What to Do About the Air Force’s Retiring F-15s

The Air Force fleet of air-to-air fighters consists of F-15, F-16, F-22, and F-35 aircraft. They are not equally capable. The F-22, a fifth-generation fighter, is most capable in this role, but the fleet consists of only 183 aircraft. The F-15 and F-16 fourth-generation fighters are more numerous, but lag in technology and are aging out. The Pentagon intends the fifth-generation F-35 to be its primary fighter for the future. However, current F-35 acquisition plans will leave the Air Force short of the number of weapons needed to decisively win the air-to-air fight envisioned above. Loss of the F-15C/D fleet is the primary driver of the looming gap.

In response, analysts have debated whether to buy more F-35 or F-15EX aircraft. The case for more F-35s goes something like this — “the synergy of stealth, fused information, and integrated automated processing” is critical to winning in highly contested threat environments. Some go so far as to claim, “aircraft without these attributes are irrelevant.” Thus, Air Force leadership has been vocal about not buying any “new old” aircraft. Critics of this approach doubt the service will get either the planned number of 1,763 F-35s or accelerated delivery, making an “F-35-only” solution unrealistic.

Those making the case for F-15EX note its high-tech upgrades over the retiring F-15C/D and inherent strength of a “diversified portfolio” of airpower, which includes fourth-generation fighters. However, the primary argument is lower cost, both in acquisition and operations and maintenance. Opposition to an F-15EX solution goes beyond skepticism of its relevance in the modern threat environment. There is concern that F-15EX funding will come from the F-35 coffer.

Capacity and the Need to Operate in Denied Environments

Meeting the air-to-air challenge requires both the technological edge needed to operate in heavily defended areas and the ability to employ forces in sufficient numbers. In other words, the Air Force needs capacity. Both the F-35 and F-15EX are multi-role, meaning neither is optimized for the air-to-air combat mission. The F-35 is more survivable and better networked, but is unable to deliver the capacity in time at achievable cost. The F-15EX can provide needed capacity sooner with lower training, maintenance, and acquisition risks. A mix of aircraft may well be the best solution, but the acquisition of F-15EX is not the only way to fill the gap.

How big is the gap? Calculating that one F-35 can carry four air-to-air missiles and an F-15C can carry eight, one analyst arrives at a need for 235 F-15EX to replace the F-15C/D and ensure the needed capacity without breaking the bank. This capacity is certainly not a steady-state requirement. What scenario would demand the Air Force generate this level of firepower? Only one: a major conflict with Russia.

I do not dispute that such a conflict would demand full-spectrum military capabilities. Nor do I advocate the Pentagon forego essential organic capabilities. The Air Force can, however, identify non-critical yet highly desired areas where the risk of outsourcing is acceptable. Capacity requirements are inherently compatible with outsourcing. After all, outsourcing capacity is perhaps the key reason the United States has allies and partners. When faced with a capacity shortfall of air-to-air weapons, outsourcing is a perfectly legitimate policy response.

Bringing in Allies

A major conflict with Russia would not be a U.S.-only affair. America would be fighting alongside NATO allies and regional partners, perhaps even allies in Asia. The air superiority capacity of partners and allies should be included in determining requirements and should be discussed publicly. The discussion should not narrowly focus on acquiring and integrating F-15EX, but should consider deeper operational integration with allies; the Air Force need not carry the full air superiority burden. A quick tally of NATO fourth-generation capacity reveals over 1,200 aircraft. Finland and Sweden — both non-NATO partners — add 10 percent to that at 126. As the National Defense Strategy notes, “When we pool resources and share responsibility for our common defense, our security burden becomes lighter.”

NATO periodically assesses the best mix of capabilities to bring to the fight. The Pentagon should accept the allies’ enduring commitment to sustaining fighter capabilities. Air-to-air ordnance capacity is a niche contribution that takes advantage of their current force structures and procurement appetites. Of course, numbers alone are not sufficient; Air Force reliance on allies to fill the gap requires strong operational concepts and frequent training opportunities.

It’s clear that conflict with Russia would demand full air superiority capacity and present the greatest demand for air-to-air weapons. However, this is the situation for which outsourcing holds the least risk. Russia’s behavior since its invasion of Ukraine and annexation of Crimea have strengthened shared security concerns among the United States, NATO, and other regional partners.

Russia’s invasion of Ukraine starting in 2014 has done more for NATO unity than any other development in recent decades. NATO’s Brussels Summit Declaration from 2018 offers a damning characterization of Russian actions. It notes that, through its aggressive actions, Russia had “reduce[d] stability and security, increased unpredictability, and changed the security environment.” Attitudes toward Russia do vary across NATO, but there is resolve regarding the need for collective defense if Russia seriously oversteps. There is more cohesion on this issue than at any time since the end of the Cold War.

Non-NATO partners in the region are also in line with NATO’s perspective. Sweden’s new white paper outlining defense strategy to 2025 explicitly identifies Russia as the primary threat to regional security. It notes that “The military-strategic situation has deteriorated over the past few years, i.e. due to political developments in Russia and Russia’s increased military capability. Russia already has a significant military capability at its disposal in comparison with its neighbors.” Even proudly neutral Sweden recognizes that “the transatlantic link plays a crucial role for Europe and for Sweden. NATO is the clearest manifestation of this link. It is of great importance that NATO assures its collective defense guarantees.”

The Air Force Does Not Need to Fill the Fighter Gap by Itself

The potential gap in air-to-air combat power, according to the Air Superiority Flight Plan, is expected by 2030. This has triggered valuable analysis and discussion that’s focused on how the Air Force alone can eliminate the gap. Some propose accelerating and increasing the F-35 buy. They see its technology as critical to success in the modern operating environment. Others argue that an “F-35-only” solution is too costly and unnecessary, instead advocating for acquiring F-15EX.

Two things stand out in this debate. First, there is an underlying assumption that the Air Force must fill the gap alone. Contrary to this assumption, allies and partners share U.S. concerns regarding the threat from Russia. They do not expect to meet such a threat alone and neither, for that matter, does the United States.

Second, despite an increasing likelihood that future conflict will be fought in denied operating environments, many airpower experts see an important role for fourth-     generation fighters well into the future. Allies have a significant number of these less expensive and easily maintained aircraft. The policy community should give serious consideration to making them a big part of the solution.

This air-to-air gap is primarily about numbers. The Air Force should develop concepts of operations using allied fighters to provide the capacity needed to win the fight. However, effective combat power and associated deterrent effect require more than concepts. The Air Force should also establish a training program and exercise regime to prepare allies and partners to fill capability gaps. Such an approach could obviate the need for F-15EX and provide a bridge to a time when the F-35 fleet is prepared to handle the task alone.


Dr. Hunter Hustus spent 34 years in the U.S. Air Force, 20 of which were in uniform. As an electronic warfare officer in the B-52, he spent six years on nuclear alert, six years in test and evaluation developing tactical doctrine for multiple combat aircraft, and four years in NATO integrating allied capabilities. As a civilian, he was the Air Force foreign policy advisor for Europe and Africa. He served the last eight years of his service at the Pentagon as a nuclear strategist, theorist, and communicator. He is now an independent consultant on strategic security issues residing in Stockholm, Sweden. The views expressed are his own and do not necessarily reflect the official policy or position of the Department of the Air Force nor that of the U.S. Government.

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