Ever since word first broke last summer that the U.S. Air Force was considering (at the Pentagon’s direction) the idea of adding a dozen or so new F-15s to their stable as part of their 2020 budget proposal, outlets have been clamoring to find ways to pit the new F-15X against America’s premier stealth fighter, the F-35.

Fans of the fifth-generation fighter of the future have repeatedly argued that devoting funding to an upgraded version of an older jet is a fool’s errand, suggesting that those funds should instead be used to expand deliveries of the F-35. Of course, these arguments consistently ignore statements made by both Lockheed Martin and Pentagon officials, which have made clear the F-15X funding will have nothing to do with the F-35. Defense pundits (and some officials) seem so eager to compare these two platforms that they forget they were actually built for very different jobs. Jeeps and Ferraris are both passenger vehicles, after all, but some situations are just better suited for one over the other.

(USAF)

Such would be the case for the F-15X, which, instead of replacing F-35s, would actually replace 30+-year-old F-15s that America intends to keep in the skies for decades to come. The new (old) fighters would boast more than five billion dollars’ worth of research and development compared to their aging kin, thanks to Boeing’s continued development and production of the airframe for sales to allies like Saudi Arabia and Qatar. The new F-15X would offer significant savings over older F-15s in terms of operating costs while bringing a far more advanced suite of onboard systems into the mix thanks to 30 years of continued advancements.

The F-15, including the new F-15X variant, are purpose-built air-superiority fighters with the singular purpose of hunting down and engaging enemy aircraft. The F-35 Joint Strike Fighter, for all its incredible capabilities, was truly designed for air-to-ground engagements. That’s not to say it couldn’t cause some real trouble for enemy aircraft, but it’s important to note the differences in what these jets were built to do, as well as the difference in the types of operations with which they would typically be tasked. The F-22 Raptor, not the F-35, is considered America’s premier air-superiority fighter; its mission would have far more overlap with the F-15X.

The F-22 is the spiritual successor to the F-15, not the F-35. (Wikimedia Commons)

But what if the United States was to find itself in a large-scale conflict that would require an all-hands-on-deck approach to air combat? If the U.S. needed to go to war with a nation like Russia (with historically capable fighters like the renowned Su-35) or China (with its fleets of stolen, purchased, or copycat fighters), the F-35 and F-22 Raptor, America’s fifth-generation fighters, would almost certainly find themselves extremely busy—and that’s where the F-15X could prove to be the F-35’s greatest ally, rather than its outdated competition.

Although the F-35’s “beast mode” or “third day of war” configuration allows for the mounting of 11 total weapons (including its cannon), it comes at the price of the aircraft’s stealth, which one could contend is the F-35’s most valuable asset. The aircraft is slower and less maneuverable than many fourth-generation fighters, but uses its low observability and network sensor fusion to spot enemy planes and engage them before they even know the F-35 is present. That doesn’t work when you cover the plane in missiles that send back a clear radar signature. As a result, the F-35 would need to rely solely on its internal weapons-carrying capacity of just four missiles.

When fully loaded, the F-35 is not a stealthy aircraft. (Lockheed Martin)

However, the far faster (and less stealthy) F-15X boasts enough hard points for a whopping 22 air-to-air missiles. The problem is, without any stealth to rely on, the F-15 would need to stick to good old-fashioned dogfighting—a skill the aircraft is particularly adept at, but that the added weight of all those weapons could seriously compromise. Fortunately, there’s a way to leverage both the F-35’s stealth and the F-15X’s deep magazine: Use the F-15X as an arsenal ship to support its stealthy compatriot.

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It would work like this: A formation of F-35s cross into contested airspace carrying a combination of air-to-air missiles and smart bombs in their internal weapon bays. They would be tasked with engaging anti-air defenses in enemy territory, converting contested regions into permissive airspace for sorties of fourth-generation platforms like the F/A-18 Super Hornet and aforementioned F-15s. However, a group of weapon-laden F-15Xs would be flying in behind the forward-advanced F-35s. As the incredibly advanced sensor suite in the F-35 identifies airborne targets on the horizon, the planes would position themselves to ensure limited risk to their aircraft while relaying targeting data to the F-15s, who could fire their weapons at targets identified by the more advanced fighters.

(Photo by Rusty Jarrett/Getty Images for NASCAR)

This would grant the F-35 the means to engage the enemy without completely depleting its internal weapon stores too quickly. In effect, the F-15X would serve as the sniper to the F-35’s spotter.

The truth of the matter is, the United States is still decades away from fielding a purely fifth-generation fighter fleet, and by the time it has made the shift, sixth-generation jets will already be making them obsolete. Such is the nature of fighter technology in the modern world. Giving up highly effective fourth-generation aircraft for the sake of added funding to the as-yet-unproven F-35 isn’t just impractical, it doesn’t acknowledge the reality of warfare or budget modeling. Winning wars is about finding the most effective ways to leverage the tools at your disposal, and teaming stealth aircraft with capable fourth-generation platforms is just one of many ways the United States can do so.