F-15X Will Come In Two Variants, And No, It Won’t Cost $100M Per Copy

Since breaking the F-15X story last July, pretty much everything our original exposé discussed has come true. After many discounted that original report, last December Bloomberg reported that the F-15X would indeed appear as a procurement program of record for the Pentagon’s 2020 budget proposal, which is due to be released at any time. Comments by heads of the USAF and industry have since confirmed this eventuality. Still, that report was thin on details, leading to quite a bit of confusion about what would be included in the USAF’s initial investment into the F-15X and what was exactly planned for the program overall. With that in mind, we have new details that answer some of these questions and paint a finer picture of what the F-15X will look like when it rolls off the production line, in one of two distinct forms, as well as what the new Eagle variant will mean for the United States Air Force. 

Editor’s note: Please read our original feature on the F-15X to understand its genesis, capabilities, and purpose, as well as this update to get up to speed on the concept if you have not already.

First off, we still haven’t seen the final draft of the Pentagon’s proposed 2020 budget. Things can change, but many of the details we are about to unveil aren’t dependent on the exact dollar figure the Air Force sets aside for F-15X. Also, I can’t stress enough that, just as I originally discussed in detail, the F-15X is not a Boeing ploy to disrupt the F-35A program. The USAF’s top uniformed officer and the CEO of Lockheed have both confirmed this as fact, echoing exactly what I wrote last summer. Many media outlets will continue to blindly pit the two programs against one another as if it is a competition, but it’s not. The USAF’s target inventory goals for the F-35 will be unaffected by the limited scope of the F-15X initiative. 

Once again, don’t take my word for this, take it from Lockheed’s own CEO, Marillyn Hewson, who said the following during an earnings call last week: 

“If they choose to have an order of the F-15, it won’t be at the expense of F-35 quantities… I’m hearing that directly from leadership in the Pentagon, and I think that’s an important point for me to make. It’s not just our suspicion, but I’ve been told that directly.”

The Air Force’s Chief of Staff, General David Goldfein, offered more detail and further underscored this reality in statements made to Defense News’s Jeff Martin: 

…Goldfein said Saturday that the decision to possibly refresh the F-15 fleet comes down to the need for more fighters in service, regardless of generation.

“They complement each other,” he said. “They each make each other better.”

When asked if that meant compromising for quantity over quality, he said that would not be the case.

“We’ve got to refresh the F-15C fleet because I can’t afford to not have that capacity to do the job and the missions.” Goldfein explained. “That’s what this is all about. If we’re refreshing the F-15C fleet, as we’re building up the F-35 fleet, this is not about any kind of a trade.”

He added that Air Force needs to buy 72 fighters a year to get to the amount they need in the future — and to drive average aircraft age down from 28 years to 15 years. And while Goldfein might want all 72 to be fifth generation F-35s, budgetary concerns likely won’t let that happen.

“If we had the money, those would be 72 F-35s. But we’ve gotta look at this from a cost/business case.” he explained. “An F-15 will never be an F-35. Never. But I need capacity.”

So, buying a few F-15Xs now to begin recapping the F-15C/D fleet, the youngest of which is now well over three decades old, will have no impact on the future F-35A force structure. The idea that advanced Eagles complement F-35s, and vice versa, isn’t just held by some in the top rungs of the USAF, either. 

Capt. Andrew “Dojo” Olson, F-35 Heritage Flight Team pilot and commander poses for a photo with Gen. David Goldfein, Chief of Staff of the Air Force, and Marillyn Hewson, chief executive officer of Lockheed Martin July 13, 2018 during the annual Royal International Air Tattoo at Royal Air Force Fairford, England. RIAT 2018. Both leaders have made statements that should dispell the impression that the F-15X will compete for funds with the F-35A. , DoD

With that out of the way, let’s talk about numbers. The December report from Bloomberg said there would be $1.2B set aside in the 2020 defense budget proposal to procure a dozen F-15X aircraft. This led many to believe the price of each F-15X would be $100M. This is more than the unit cost of an F-35A, which is slated to hit $80M apiece in the not so distant future. 

According to sources close to the discussions, this is flat out incorrect. The money being set aside in 2020, possibly around $1.1B, will include an initial order for F-15Xs—likely eight aircraft—with the rest of the money being spent on non-recurring costs, including setting up and managing the program and to pay for a relatively tiny amount of development work needed to bring the aircraft’s systems and software in line with the USAF’s exact specifications. 

Keep in mind that this relatively minuscule developmental cost is only possible because other countries have spent roughly $5B over the last couple of decades to continuously evolve the F-15 into what it is today. So basically, the USAF is getting this for free. In contrast, bringing an all-new fighter into existence costs tens of billions of dollars in development work that spans decades. 

The big question then is how much will these jets cost? Our sources familiar with the discussions say they will cost “less than an F-35 is ever forecast to cost, best case,” let alone what it is priced at now. This indicates that Boeing is going to cut the USAF one hell of a deal on these jets, which will help keep the F-15 production line open and Boeing’s historic St. Louis plant building fighters well into the latter half of the next decade. This assessment is based on the Office of Cost Assessment and Program Evaluation’s (CAPE) numbers, not just some blue sky pitch from Boeing. 

These numbers are not projected from hypothetical notions or the dreams of consistently large buys materializing down the line, they take into account hard data from aircraft already being rolled off the production line and flying around the globe. This is the same for the F-15X’s projected cost per flight hour that will be spread across the airframe’s whopping 20,000-hour design life. For reference, most tactical fighters have a design life of around 8,000 hours

F-15 Advanced, pictured here, has close ties to the F-15X concept being offered to the USAF, Boeing

In addition, the F-15X was offered by Boeing to the USAF under a firm, fixed-price contract terms. In other words, if the USAF executes the offer, and the aircraft cost more than what is estimated, Boeing eats that cost directly, just as it has with the KC-46 tanker. There is nearly zero financial risk to the USAF. What it agrees to spend on procuring the capability is exactly what the bill will look like in the end, unless the two parties decide otherwise.

Boeing has been especially aggressive with its bidding on aircraft programs using similar constructs as of late, snapping up the UH-1N replacement contract, MQ-25 carrier-based tanker drone tender, and the opportunity to build the USAF’s next jet trainer.

Maybe what’s more important, is that the F-15X is being designed specifically to slot directly into the USAF’s deeply established F-15 infrastructure, even down to seamless pilot conversion. Our sources say it will only take one or two flights per F-15C pilot to convert to the F-15X for the air superiority mission, saving millions on retraining aircrews, not to mention ground crews, that are already intimately familiar with the Eagle. But there are other factors as well. 

Some information about the proposed F-15 Advanced. The F-15X will have near identical features but will be offered in single and two seat configurations. , Boeing

Converting a fighter unit to any new airframe costs a lot of money. The unit cost is just the ‘cover charge’ compared to what it costs to bed-down and sustain the type over its service life at multiple locales around the globe. New infrastructure has to be built or old infrastructure adapted, and this is especially costly when introducing stealthy 5th generation fighters. Support systems, tools, and parts needed to keep the jet in the air also have to be purchased, which quickly adds up. And above all else, the unit has to be relegated to a reduced or unavailable readiness status during much of the long conversion process, which can last years.

All this results in something of a logistical nightmare, especially when you take into account the fact that the USAF’s tactical jet inventory is a shadow of what it was just a decade ago, all the while demand for its capabilities have jumped dramatically. Also, the majority of the F-15C/D units that would get F-15X have to provide multiple aircraft and crews at all times to the critical homeland defense alert mission. But none of these capacity issues will happen if F-15C/D units convert over to the F-15X. As the new airframes are added, a unit’s readiness should actually go up substantially along with overall their warfighting capability. 

Even if the USAF could buy 100s of F-35s a year, they simply couldn’t convert squadrons fast enough while maintaining any sort of a minimum combat capacity. In other words, production levels are only one part of the story, the ability for squadrons to absorb those aircraft is another. By buying a lot of F-35s each year and some F-15Xs, this issue is mitigated to some degree as the USAF can get new fighters into the fight without having to tank its overall readiness, which isn’t in a good place as it is. In fact, in many ways, the F-15X actually takes a lot of pressure off the F-35 as it continues to teethe its way into a position as America’s predominate front-line fighter capability. 

All this is largely validated by General Goldfein’s comments about capacity and the realities he is facing with his current fighter inventory force structure and the demands being placed on it, both operationally and fiscally. This all comes at a time when the USAF is also chasing its new and highly ambitious 386 squadron goal. 

Air Force Magazine recently inquired to Air Force Undersecretary Matt Donovan about the F-15X. Although he wouldn’t address the initiative directly, he did paint a picture of the logic behind it: 

“History being what it is, and because we never quite got to the procurement ramp we needed to” on the F-35, “we’re in a bit of a pickle,” Donovan said. “We don’t have the capacity we need” in the fighter force. Donovan’s speech to the AFA audience focused heavily on the need to increase the size of the Air Force to 386 combat squadrons in order to fulfill the National Defense Strategy of engaging China and Russia in Great Power Competition.

He noted that, under original plans, USAF expected to have 736 F-35s by now, but “we have 174, … so … we need to increase our fighter procurement, replacement rate.”

Every F-15C/D left in the USAF’s inventory is at least 33 years old, yet even these jets have availability rates that are markedly higher than what’s found in the F-35 community. , USAF

As for how many jets would be procured under an F-15X initiative, our sources close to the discussions say between 150 to 250 aircraft depending on what the USAF wants to do with its overall force structure. The most likely number is roughly 230 airframes to replace the F-15C/D force one a one-for-one basis. Procurement would likely start with eight aircraft, which could be delivered very soon, with roughly 18 to 24 procured each year after that. Oh, and there are two variants of the F-15X that are being offered by Boeing and will likely be procured. One is dubbed the F-15CX and the other is known as the F-15EX.

The F-15CX will be a single-seat configuration, while the F-15EX will be a two-seater with a fully missionized rear cockpit complete with a wide-area flat panel display, helmet-mounted display, and full flight controls. The F-15EX will cost a couple million dollars more than its single seat stablemate, but they will roll of the St. Louis production line right alongside one another. 


The F-15EX can be used for training or for actual missions where having two crew would be beneficial. As discussed in great detail in my original F-15X feature, an F-15X could serve as a unique platform for various missions in the future beyond the currently established mission set serviced by the F-15C/D community. These include acting as a flying weapons truck and carrying outsized weapons, including hypersonic cruise missiles and very-long-range air-to-air missiles, to controlling flocks of stealthy unmanned combat air vehicles, to acting as a network relay between 5th generation and 4th generation fighters, as well as other assets in the battlespace. With this in mind, having a second crew station that can accommodate many operational contingencies in the future is likely to be highly attractive. 

Still, this doesn’t mean that F-15X users will hop into complex air-to-ground and other mission sets when the aircraft are delivered. The jets will be used primarily as an air-to-air weapon system just like the aircraft it replaces, the F-15C/D. But, according to our sources, adding GPS guided air-to-ground munitions, just like what was done in the similarly air-to-air focused F-22 Raptor community, would give the F-15X added versatility at virtually no cost and without detracting heavily from training for the counter-air mission. 

The weapons configuration options for the F-15 Advanced, a concept with close commonality with the proposed F-15X. Amber launch racks could further increase air-to-air missile carriage capabilities. , Boeing

Even using the F-15X to fire advanced High-Speed Anti-Radiation Missiles to quickly knock down enemy emitters that threaten it and the aircraft it protects could also be done without significantly dulling-down the F-15C/D community’s air superiority focused role. The bottom line is that the jet will be delivered capable of virtually every fighter role imaginable, but training and fighting doctrine will dictate its actual use. 

The F-15X will have a gross weight of 81,000lbs and will be powered by either General Electric F110-GE-129 or Pratt and Whitney F100-PW-229 turbofan engines, both of which are in the 29,000lb thrust class. 

Some configuration and range information with for the F-15 Advanced, a concept that shares close commonality with the proposed F-15X., Boeing

One of the biggest issues some seem to have with F-15X is that the USAF’s decision to procure it was not based on some type of open fighter competition. But as our sources close to the discussions note, the USAF isn’t buying some new fighter to fulfill a new role. It is replacing tired F-15C/Ds that will require tens of millions of dollars in enhancements to stay flyable and tactically viable in the decades to come with new-build F-15s that are just about as off the shelf as one can imagine. It’s akin to the USAF directly replacing F-16A/Bs with F-16C/Ds.

Still, the flying service’s seemingly bold decision to face the damning fleet issues it is facing and look outside the F-35 procurement box for tactical jet solutions is bound to be met with controversy. Also, keep in mind that the USAF’s F-15X wishes have to make it through the beltway intact to become a reality, and that’s if they do emerge as expected in the fiscal year 2020 defense budget. As always, there is also another side to the story, one that is worth discussing in greater detail. 

Now that we have more information about the F-15X in hand, we will look deeper into alternatives to it and address the question of if procuring it is really a good route for the USAF to take at this time.  

Keep an eye out, we should have this follow-up piece published soon.

Contact the author: Tyler@thedrive.com

Tyler Rogoway


Tyler's passion is the study of military technology, strategy, and foreign policy and he has fostered a dominant voice on those topics in the defense media space. He was the creator of the hugely popular defense site Foxtrot Alpha before developing The War Zone.