Last week, the aerospace-defense community was overwhelmingly intrigued by a report from Defenseone.com that said Boeing was pitching a new variant of its 45-year-old F-15 Eagle line of fighters to the United States Air Force. Still, next to nothing is known about this initiative, including where it came from and what it entails exactly. Although it has been framed as a Boeing solicitation to the USAF, the opposite is actually true—the USAF began the discussion over a year and a half ago. Since then, ongoing talks have been kept incredibly hush-hush, along with the details of the aircraft involved—until now.

According to sources familiar with the discussions, The War Zone has learned about the F-15X's origins, its intended capabilities and features, and where it would fit inside the USAF's tactical airpower ecosystem.

Tyler Rogoway/Author F-15Cs execute a mock alert scramble.

USAF Looks Back To The Future The F-15X came out of a quiet USAF inquiry to Boeing and Lockheed Martin about fielding an aircraft that could seamlessly plug into their existing air combat infrastructure as part of better-defined high-low capability mix strategy—one intended to specifically help counter the service's shrinking force structure. The airframe would have to be cost-effective both in terms of operation and acquisition, very low-risk, and most of all, it would need to be non-disruptive to the larger F-35 procurement initiative. If anything else, it had to be seen as complementary to the F-35, not as an alternative to it.

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The USAF has not procured a 4th generation fighter since 2001. This was over 15 years before the discussions that led to the F-15X began. For a decade and a half, USAF brass had been adamant about only buying stealthy 5th generation fighters to fill out its tactical jet ranks. Even upgrading or retaining existing and battle-proven fighter platforms was in question early in the current decade as the service was myopically focused on stabilizing the F-35 program. Tightened defense budgets under sequester didn't help with the situation, either. As time moved on, it became clear that the F-35 might not be the USAF's one-size-fits-all solution some thought it would be. This is not a mark against the F-35, but just the reality that the USAF has tactical air power needs that don't necessitate or even benefit from the F-35's unique and costly capabilities.

USAF The last F-16 delivered to the USAF was contracted in 2001. A handful of F-15Es was also ordered that year to replace lost aircraft. They were the last 4th generation fighters the USAF has bought.

So the F-15X initiative is not some cold-call Boeing pitch, it was born out of hundreds of ever-strengthening discussions between various stakeholders within USAF and the aircraft manufacturer. All parties involved had worked hard not to disclose the talks out of respect for ongoing procurement programs and the USAF's stated needs. Additionally, doing so without providing adequate detail would surely result in the F-15X being misconstrued by the press as being some huge challenger to the F-35, when that was never actually the case or the scope of the proposed initiative. The F-15X Concept Is Born The result of those discussions is the F-15X. Our sources describe the aircraft as a single seat variant of the latest F-15 advanced Strike Eagle derivative—the F-15QA destined for Qatar—but it will also integrate many of the features and upgrades that the USAF intends (or intended as it may be) to include on its nearly four-decade-old F-15C/D fleet. And no, the aircraft is not a repackaging of the semi-stealthy F-15 Silent Eagle concept that Boeing floated nearly a decade ago. The F-15X features no low-observable enhancements of any kind.

Boeing rendering F-15X is an outgrowth of the latest export Strike Eagle derivatives and the upgrade pathway the USAF has devised for its decades-old F-15C/D fleet. It also draws on past concepts like the2040C F-15 configuration seen in this image and in the banner image at the top of this article.

The F-15X configuration is impressive as it includes a flat-panel glass cockpit, JHMCS II helmet mounted display (HMD), revised internal wing structure, fly-by-wire controls, APG-82 AESA radar, activation of outer wing stations one and nine, advanced mission computer, low-profile heads-up display, updated radio and satellite communications, the highly advanced Eagle Passive Active Warning Survivability System (EPAWSS) electronic warfare and electronic surveillance suite, Legion Pod-mounted infrared search and track system (IRST) and the list goes on.

With the help of the company's new AMBER missile carrying racks, the F-15X will be able to carry a whopping 22 air-to-air missiles during a single sortie. Alternatively, it could fly with eight air-to-air missiles and 28 Small Diameter Bombs (SDBs), or up to seven 2,000lb bombs and eight air-to-air missiles. We are talking crazy weapons hauling capabilities here. Keep in mind that the F-15C/D Eagle can carry eight air-to-air missiles currently, and the penultimate Eagle variant that is currently being built, the F-15SA, can carry a dozen.

What the F-15X doesn't include is a high price. The War Zone has learned that Boeing intends to deliver the F-15X at a flyaway cost well below that of an F-35A—which runs about $95M per copy. And this is not just some attempt to grab business and then deliver an aircraft that costs way more than promised. Our sources tell us that Boeing is willing to put their money where their mouth is via offering the F-15X under a fixed priced contract. In other words, whatever the jets actually end up costing, the Pentagon will pay a fixed price—Boeing would have to eat any overages.

This is possible because the F-15 is a very known commodity as it has been in production for 45 years and has flown hundreds of thousands of hours in continuously more capable configurations. Additionally, foreign customers have paid for the jet's advanced development already, with around $5B already spent by international operations on evolving the aircraft over the last decade and a half.

Tyler Rogoway/Author A South Korean F-15K Slam Eagle departs on a Red Flag sortie.

Boeing is also likely apt to make the Pentagon a heck of a deal on the F-15X as it will help ensure fighter production at the company's storied St. Louis plant for years to come and it would keep the door open for additional foreign Eagle orders. It would also provide an ongoing tactical aircraft production relationship with the USAF. This relationship could also be sustained via the T-X contract that aims to replace the USAF's half-century-old T-38 Talon jet trainers, but who exactly will win that contract remains a question mark as the award isn't slated to arrive until late this Summer at the earliest. Trading In The Old For The New The biggest question most have about the F-15X is where would these fighters be inserted into the USAF's existing force structure? The answer to that, and the whole impetus behind the F-15X program, has been made clear to us—the jet is intended t directly replace the USAF's entire F-15C/D fleet. It would have no impact on the existing F-15E Strike Eagle fleet or its planned upgrade pathway that is underway now. Currently, the F-15C/D force is largely arrayed along America's maritime borders, with five Air National Guard units flying the type. A squadron at RAF Lakenheath in England and two squadrons at Kadena Air Base in Japan round out the full front-line force. A small number of F-15C/Ds are also assigned to test, evaluation, and tactics development units, and a single schoolhouse based at Kingsley Field in Oregon provides "Eagle Drivers" to the fleet on roughly 235 'air superiority Eagles' in all.

Tyler Rogoway/Author A 173rd Fighter Wing F-15C taxis back to its parking spot at Kingsley Field in Klamath Falls, known inside the USAF as the "the land of no slack." The unit is the USAF sole F-15C/D training squadron and is renowned for producing some of the world's best fighter pilots.

The fate of the F-15C/D within the USAF ranks has been in doubt for over a year now, with the USAF evaluating if it will continue to deeply upgrade and eventually basically rebuild its existing decades-old F-15C/D force or if it will replace them entirely with upgraded F-16s. In fact, just last May, reports surfaced that indicated the USAF had all but formally announced that they will draw-down and retire the F-15C/D fleet. Swapping F-15s for F-16s means a capability deficit in almost every regard. Even if the USAF wants to do this it will likely result in a major dogfight on Capitol Hill. But replacing the old F-15C/D fleet with drastically enhanced F-15s could alleviate this major stumbling block and prove to be a much more attractive option.

Tyler Rogoway/Author The USAF's F-15E fleet would not be unaffected by the F-15X plan.

Even if the F-15X is cheaper than an F-35 and ends up being closer in price to a late-block Super Hornet (around $65M), the money will have to come from somewhere to acquire the fleet. But spending money now to acquire F-15Xs may actually save money in the long run. The USAF already intended to upgrade its F-15C/D fleet so that it could remain viable into the 2030s and possibly well beyond. Doing so would cost many millions of dollars per jet, especially if those aircraft end up needing new wings in the coming decade, which according to most accounts, they will. And then you still have an airplane that is in the back-half of its service life and costs more to keep in the air than a totally fresh jet. The F-15X will have a 20,000 hour service life. Yes, you read that right, 20,000 hours—pretty much three times that of most fighters being produced around the globe. As such, a new F-15X can serve for roughly 80 years. When you spread the cost of the jet over all that flight time, it does appear to be a comparative bargain.

Boeing Boeing had marketed a version of the F-15SA as the F-15 Advanced, but the single seat F-15X will incorporate many of the latest export Eagle capabilities along with the upgrades that were intended for the USAF's aging F-15C/D fleet.