F-15EX Could Replace Strike Eagle Fleet, in Addition to Older C/D Models, USAF Says

The Air Force may replace its 218 F-15Es with F-15EXs, which could expand the new program to over 400 aircraft, according to service documents justifying the sole-source contract to Boeing. The Air Force also claims buying the F-15EX will save some $3 billion in military construction and support costs versus buying more advanced F-35s.

The revelations and assertions were contained in an F-15EX Justification and Approval (J&A) document, which was dated March 2018 but not released until mid-July, to coincide with the sole-source award to Boeing of the first F-15EX contract. The program, as it’s currently structured, could be worth up to $22.9 billion if all options are exercised.

The heavily redacted document notes that the contract for Boeing posits a “rough order of magnitude” purchase of 200 airplanes, but the “most probable quantity” would be 144 fighters. However, it also notes that while the program is “initially” intended to refresh the aging F-15C/D, a decision to similarly replace the F-15E Strike Eagle fleet with the EX “has not been made, but remains an option.”

An Air Force spokesman said the Air Force’s position on the F-15E hasn’t changed.

“That decision has not been made,” the spokesman said. “Air Force leadership will determine that. The F-15E will continue to perform its mission for the foreseeable future.” The spokesman was not immediately able to say if the Air Force is conducting an analysis of alternatives regarding replacement of the F-15E fleet.

The Air Force fields about 234 F-15C/Ds, which are dedicated to air superiority, and 218 F-15Es, configured for ground attack while retaining air-to-air combat capability. Boeing recently described the F-15EX as a “multirole” aircraft. The Air Force’s previous statements that it is seeking up to 200 F-15EX to refresh the F-15C/D fleet indicates it is not planning to replace the Eagle on a one-for-one basis.

Plans dating back to the early 1990s called for the F-15C/D to be replaced by the F-22, but that aircraft’s production was terminated prematurely by Defense Secretary Robert M. Gates in 2009, at less than half the planned inventory of 381 airplanes. Former Air Force Chief of Staff Gen. Mark A. Welsh III subsequently said the F-35 would have to pick up some of the air superiority mission, given the age of the F-15 and its looming retirement.

The F-35 was planned to replace the A-10 and F-16 in USAF service, while the F-22 was to replace the F-15C/D and the F-117 in the stealthy strike role. The Air Force has never identified publicly how it planned to replace the F-15E. Production of the E-model followed the C/D by almost exactly 10 years, so the F-15E will likely start reaching its planned retirement age in the early 2030s. The E-model was strengthened in some ways over the C/D version to help it sustain heavier loads.      

The J&A document makes the case that the F-15C/D fleet is becoming unsafe to fly, and that a service life extension program would not be cost-effective. The document places a premium on speed-to-service, saying that no other company could produce a new fighter to replace the F-15C/D in a timely manner, and that it would take years to qualify a second source besides Boeing to make F-15s.  

The service can “leverage” the several billion dollars of investment of other F-15 customer countries, such as Saudi Arabia and Qatar, in advanced versions of the Eagle. The J&A document quoted the F-15 system program office as saying the EX will enjoy “90-95 percent commonality” with the F-15QA for Qatar.

The service asserted that wargaming and operational analysis shows that “a mix of fourth-generation capacity and fifth-generation capability is necessary in balancing near- and mid-term readiness with future needs.” USAF has “further concluded that performing a refresh of the existing F-15C/D fleet [long redaction] is the only way to improve readiness and to maintain the USAF fighter aircraft capacity.”   

Making a virtue of necessity, the Air Force also argued that the EX saves money over buying the F-35, setting aside the differences in their capability.

“Utilizing a different airframe that is currently in production would require a cost-prohibitive and time-consuming effort to replace the existing F-15 air combat infrastructure,” the Air Force said in the justification. “Indeed, the USAF estimates that refreshing the F-15C/D fleet with F-15EXs will save USAF $3 billion over the FYDP [Future Years Defense Program] compared to replacing the fleet with F-35s, by avoiding significant transition costs required for a new aircraft (i.e., MILCON, aircraft-unique facilities, operator and maintenance transitions costs, etc.).”

USAF estimated it will take “six months or less to transition from the F-15C/D to the F-15EX” given the commonality of the aircraft, their components, and ground support equipment, while transitioning from “F-15s to the F-35 (or any other airframe) will take approximately 18 months for an Active-duty squadron and 36 months for an Air National Guard squadron.” The document also emphasizes that, “no other aircraft will satisfy the USAF requirement to refresh the F-15C/D fleet.”

The Air Force never planned to resume buying the F-15 and did not initially request the F-15EX, preferring to stick with the stealthy, fifth-generation F-35. Former Chiefs of Staff Gens. John P. Jumper and T. Michael Moseley rejected buying “new-old” F-15s during their tenures. USAF’s current Chief of Staff Gen. David L. Goldfein has said on numerous occasions that the EX must not come at the expense of the F-35.

The EX was added to the Air Force’s budget by former Defense Secretary James N. Mattis at the urging of the Pentagon’s Cost Assessment Program Evaluation shop. Pentagon sources have said Mattis and other officials felt the F-15EX could serve as a competitive lever to pressure Lockheed Martin to reduce operating and acquisition costs on the F-35. While the F-15 costs more per copy than the F-35, its operating costs are pegged at $27,000 per hour versus $35,000 per hour on the F-35. The F-35 Joint Program Office says it has a plan to get the F-35’s operating and sustainment costs down to $25,000 per hour by 2025.

Boeing’s X-32 contender in the “winner take all” Joint Strike Fighter competition lost out to Lockheed Martin’s X-35 in 2001. At the time, members of Congress with Boeing constituencies argued that Lockheed, then also making the F-22, shouldn’t be the sole builder of advanced combat aircraft. They urged that Boeing should be given some of the F-35 work, but the Pentagon view prevailed that Lockheed had structured its winning bid with a certain team, and Boeing was not on it. The Pentagon said Boeing’s continuing work on the F/A-18 for the Navy and Marine Corps, coupled with residual orders for F-15s overseas and work on the stealthy Joint Unmanned Combat Aircraft System, would keep it in the running for a future USAF combat airplane competition in the 2025 timeframe.

Boeing is building the MQ-25 unmanned tanker aircraft for the Navy as well as the T-7A advanced trainer for the Air Force.

The Air Force is also pursuing the Next-Generation Air Dominance airplane, and the uninhabited Low-Cost Attritable Aircraft program, expected to yield operational air combat assets in the 2030 and 2026 timeframe, respectively.