Exclusive: Unmasking The F-15X, Boeing's F-15C/D Eagle Replacement Fighter

Boeing and the USAF have been in talks for a year and a half about replacing the aging F-15C/D with a brand new advanced Eagle derivative, the F-15X.

Boeing

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.

USAF

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.

In addition, our sources tell us that F-15X cost-per-flight-hour has been deeply investigated both by Boeing and by third parties by leveraging metrics from legacy F-15 operations and those of late-model Strike Eagle derivatives and even other fighters in the USAF's inventory. The final figure is said to be around $27,000 per flight hour. This is far less than the aging F-15C/D's hourly operating cost (about $42,000 per hour) and about $6,000 more than what the USAF is paying to fly their largely middle-aged F-16 fleet today. 

Compared to the F-22 or F-35 this figure is very attractive as well. Apparently, it also takes into account a single-seat, multi-role mission set similar to an F-16 and the manning demands associated with it, not just an air superiority role. And once again, because the F-15 is a known commodity, this number is not some optimistic guess.

With all this in mind, the business case for the F-15X is that the jets will pay for themselves in about a decade's time based on operational cost savings over their F-15C/D brethren—the last of which was built in 1986—alone. 

The Seamless Integration And Plenty Of Production Capacity

It's also worth noting that the cost of an aircraft's development—which in this case is nothing—and its 'flyaway price' tell just part of the fiscal story. New logistics chains, centralized sustainment facilities, training squadrons, the unique infrastructure required at every base a new fighter is stationed, program offices, operational test and tactics development, weapons integration, and so on are all extremely expensive but seldom discussed aspects of introducing a new fighter aircraft. The F-15X is specifically configured to require none of this. 

It slots directly into the USAF's existing Eagle infrastructure down to the using the same ground support equipment as its F-15C/D and F-15E predecessors. Even pilot training is said to be seamless, with it supposedly taking just single sortie, a bit of class work, and a couple simulator hops to convert an existing Eagle pilot over to an advanced Strike Eagle derivative. It is truly a plug-and-play concept above all else.

Tyler Rogoway/Author

The flight-line of the 142nd Fighter Wing. The F-15X will be able to leverage the F-15C and F-15E's infrastructure.

The F-15X could also allow current F-15C/D units to migrate to multi-role mission sets instead of the strictly air-to-air mission that they have traditionally performed. The F-15QA will be capable of deploying close to every weapon in the Pentagon's tactical fighter weapons inventory and so will the F-15X. This includes weapons like JSOW, Harpoon, and even HARM. But once again, taking on new missions can be done selectively and F-15C/D units could just as well continue concentrating on air-to-air combat exclusively. 

Yet even a suppression/destruction of enemy air defenses (SEAD/DEAD) role that leverages the F-15X's powerful electronic warfare and electronic surveillance measures suites, along with new weapons like JSOW and HARM, would fold nicely into the 'Gray Eagle' community's counter-air role. 

As for how quickly the USAF could obtain F-15Xs to replace its F-15C/D fleet, that is really up to the USAF. It is known that the F-15 production line is quite elastic and could scale up to dozens of jets a year if the demand was there. Currently, Saudi Arabia's Eagles are being built and/or refurbished into the F-15SA configuration and soon the first of Qatar's 36 F-15QAs will begin production. It is likely that Qatar will also execute an option for another 36 Eagles as well. 

Another order for F-15s from Israel is more likely to occur than not at this point, and other prospects for export remain, from Europe to Asia. But getting the USAF back on the pages of the Eagle's order books would be a huge coup for the program and it alone could very well lead to additional foreign orders. 

The Heavyweight Of Tactical Aerial Weapons Platforms

The F-15X initiative may be all about getting already available capabilities to the USAF at a low cost with next to no fuss, but in the future, the jet could play a pivotal role in supporting many of the most buzz-worthy air combat concepts being discussed by USAF today. These include man-machine teaming, in which the F-15X would play quarterback for stealthy unmanned combat air vehicles (UCAVs) that can go where even the F-35 and F-22 cannot. 

The F-15X could also act as a weapons truck for stealthy fighters operating forward of their position into more highly contested airspace. This will become an especially critical capacity as ultra-long-range weaponry becomes too large for stealth fighters' weapons bays or to be carried in relevant numbers by smaller fighters. 

In the decades to come, it's very likely that standoff tactical jamming support will be necessary to ensure the survivability of America's current cadre of narrow-band low-observable fighters. The E/A-18G Growler provides this to a certain degree today, but additional capability organic to the USAF could come via F-15Xs outfitted with jamming pods or conformal jamming arrays installed in modified conformal fuel tanks/fast packs. This mission could benefit from the F-15's long-endurance as well.

Public Domain

Fast Packs were originally envisioned back in the 1970s as having many more uses than carrying additional fuel. This adaptability is still a largely untapped resource for the Eagle family, especially in an age of conformal arrays and increasingly miniaturized sensor and even directed energy systems. 

Directed energy weapons—namely lasers—and large surveillance sensors, and even outsized anti-ballistic missile weaponry, would be at home on the F-15X more so than virtually any other fighter. The jet's legendary ability to lug large payloads over long distances to execute standoff attacks could also be very beneficial, especially considering how vulnerable tanker aircraft are increasingly becoming—a problem that is only slated to get worse in the future. A fighter with a larger combat radius that can carry more weapons to hit more targets than its stablemates equates to enhanced survivability for tankers that support them and less dependence on them in general. 

An Eagle Encore's Feasibility

As far as how serious the USAF is about actually acquiring the F-15X as an F-15C/D replacement, sources familiar with the ongoing discussions indicate that the service is very serious about it. And frankly, the powers that be need to make a decision about the F-15C/D's fate as spending billions upgrading the fleet just to retire it from service in a few years time makes no sense and is incredibly wasteful.

Above all else, the reality that the F-15X concept is actually a thing, and has been in the works for the better part of two years no less, is a promising indication that the USAF is coming to terms with the need to field a diverse mix of tactical fast-jet capabilities, with each platform bringing something special to the table. An all stealth force sounds good, but in reality, it is fiscally unsustainable and not beneficial, and even a hindrance, to many of the missions the USAF conducts on a daily basis and will continue to do so for decades to come. The Eagle's (old or new) heavy lifting and long endurance capabilities alone are somewhat indispensable in regards to where the future of air combat is headed. 

NASA

The F-15 is the heavy lifter of the USAF's fighter cadre. It has been used to launch anti-satellite weapons and for tests with outsized missiles, including the AIM-54 hypersonic test missile as seen above. There have even been concepts that envisioned the F-15 carrying Patriot missiles aloft for anti-ballistic missile duties. 

In the end, when it comes to the USAF's tactical airpower needs, it needs to invest in narrow-band low-observable fighters, deep-penetrating wide-band low-observable UCAVs, and non-stealthy fighters that can lug a lot of weaponry over a good distance and/or provide economical solutions for the USAF's 'bread and butter' fighter missions. You don't need an F-35 to take out a Taliban opium lab or to sit alert duty day in and day out to guard America's sovereign airspace

And this is what the F-15X is all about. It's a non-risk, relevant, and supposedly cost-effective solution to a lot of the USAF problems. And once again, it is not meant to compete in a big way with the F-35 program.

The recent precedent of the U.S. Navy placing substantial advanced Super Hornet orders—which can be at least partially attributed to the Trump administration's intent to spread the wealth around when it comes to Pentagon fighter procurement and its overall push for a larger defense budget—also gives additional credence to the F-15X concept. 

Boeing

Block III Super Hornet

In the case of the recent advanced Super Hornet's orders from the Navy, it's not as if the service canceled the F-35C—which will attain initial operating capability next year. It just came to terms with the fact that buying more Super Hornets now alleviates risks that have manifested themselves in the F-35 program and above all else, doing so relieves pressure on the Navy's buckling fighter fleet. 

The act also helped out with alleviating USMC's own fighter woes as it allows for younger Navy F/A-18Cs to be transferred to the USMC, many of which will receive substantial upgrades of their own. And enhanced Super Hornets and F-35Cs will complement each other nicely on many levels for decades to come. In other words, both fighters can coexist in production. It doesn't have to be an 'all or nothing' proposition as so many have tried to instill over the last decade or so.

As to whether or not the USAF should actually move forward and procure the F-15X as a direct F-15C/D replacement, we'll save our analysis for an upcoming post. But the concept is certainly enticing and it is more relevant now that it would have been a decade ago when the USAF saw stealth as a threshold qualifier for nearly all front-line future fighter operations. 

We will keep you in the loop as we learn more about the F-15X and its potentially bright future within the ranks of the USAF.

Tyler Rogoway/Author

Contact the author: Tyler@thedrive.com