The United States Air Force maintains the largest and most technologically advanced air force in the world. Attaining and maintaining air superiority has been a top priority of U.S. military leadership since World War II. This has resulted in a never-ending pursuit of advanced technology to deal with the current and projected enemy threat.

Recently, a proposal has been put forth to produce a variant of the F-15 to add to the United States Air Force’s current fighter inventory. To some, this has resonated positively. However, upon further investigation, the rationale and validity of this proposal fall apart.

s a former F-15 pilot, I love the aircraft. It was my first and the only front-line fighter I flew throughout my 40-year career and 2500 plus F-15 flying hours. It pains me greatly to write this article, but decision makers must accept what I have – the F-15’s air superiority days have come and gone! The 5th generation era has arrived, and the global near-peer threat is evolving to meet that capability.

The F-15 Eagle, designed in response to the Air Force’s requirement for an aircraft dedicated solely to the air superiority mission, was first flown in the early 70s. Like the P-51 and the F-86, that were the greatest air superiority fighters of their generation, the F-15 was the greatest air to air fighter of its generation – the 80s and 90s. However, like the P-51 and the F-86, the F-15 has been surpassed by a more capable fighter. Like it’s legacy aircraft counterparts, the F-15 is a fighter built for the threats of its timeframe – the 20^th century. Not a fighter built in anticipation of what capability and survivability would be needed in the 21^st century.

The average age of U.S. Air Force aircraft, including fighter jets, is currently at a record-setting rate due to restrictive defense budgets of past administrations. Therefore, it is more imperative than ever for the USAF to replace the aging fleet with the most technologically advanced, survivable fighter that delivers the maximum performance within budget allocations, and more importantly, that can continue to be modernized with leading-edge technology.

Wisely, the U.S. Air Force has invested in the F-35 Lightning II, the most advanced stealth multi-role operational fighter aircraft in the world. This 5^th generation aircraft is transforming air combat with distinctive speed, range and weapons capacity coupled with stealth, sensor capability, information fusion and network connectivity that brings unprecedented capability to warfighters. 

Chinese and Russian Surface-to-Air and Air-to-Air threats are proliferating in quantity, advancing in capability and being deployed to critical areas of U.S. interests. To survive in the modern battlespace, a fighter must have stealth, advanced 360-degree sensor capability, advanced electronic warfare, and the ability to connect to sea, air, and space assets. The F-35 does all of these things – the F-15x can do none of them.

Some say 5^th Generation fighters make 4^th Generation fighters better; this is true, but the corollary is true that while protecting 4^th Generation fighters, 5^th Generation fighters are sub-optimized. Where 4th generation fighters are forced to adapt to an advancing battlespace, the F-35 was specifically designed to operate in it. With stealth, electronic avionics systems and infrared sensors – capabilities the F-15 does not have – the F-35 defines the battlespace that adversaries are striving unsuccessfully to adapt to.

For those in favor of bolstering 4^th generation aircraft for Homeland Defense, they need to keep in mind that in the worst case scenario of an attack on our homeland, we will see highly advanced enemy 4th generation aircraft and even 5th generation aircraft.

The 5^th generation fleet is growing as the F-35’s capabilities are proving reliable where it matters most for the U.S. Air Force:

• The F-35 fleet is growing at a pace unmatched by any fighter in the world. By 2023, about 1,000 aircraft will be operating from over 40 bases and ships. In less than six years, more than 600 aircraft will be integrated into global operations, while supporting the stand up of about 25 additional bases and ships.

• The F-35 weapons system reliability continues to improve, and newer jets are now averaging greater than 60% mission capable rates. A number of operational F-35A squadrons have nearly 70% mission capable rates, which are among the highest in the USAF fleet.

• By 2023, the F-35’s will have Technology Refresh 3 capability, which will further widen the capability gap between F-35s and 4th generation aircraft.

Today’s battlespace is a complicated multi-domain fight with space, air, ground and cyber assets. Only the F-35 can lead this modern battlespace in capabilities and modernization, and remain within budget allocations.

Faced with funding shortfalls and sequestration, the Air Force opted to continue 4^th generation investments because the threat environment allowed it, and the cost to acquire and to operate legacy jets was much more affordable than advanced capability aircraft like the F-35. That is no longer the case.

The price of an F-35A is now $90 million, which is less than the reported price that the political leadership of the Pentagon will reportedly pay for legacy generation fighters – and the operations cost has started down the same cost reduction curve that the unit cost has already demonstrated. Recent international competitions and DoD analysis have shown that all 5^th generation fleets will be more cost-effective than mixed fleets.

Additionally, just as the government and industry drastically reduced F-35 production costs, F-35 sustainment is also estimated to be reduced by more than 40 percent.

Though the F-35 program has been criticized in the past on cost – as traditionally occurs with new military programs – by 2025 the cost to operate an F-35 per year is expected to be about equal to any 4^th generation fighter – including the F-15. Also by 2025, the F-35 is anticipated to cost $25,000 per flight hour – which is equal to or less than any 4th gen fighter. Additionally, while some have reported the actual cost to acquire the F-15X will be $80 million – this is without any external sensor pods, targeting pods and pylons to carry weapons and fuel.

F-15X advocates have stated that the aircraft will cut operations and sustainment costs in half compared to the F-35; however, that is not necessarily the case. First and foremost, buying new F-15s will require the Air National Guard to maintain multiple aircraft sustainment systems for decades to come, rather than eventually sun setting their F-15s all together and only paying to operate and sustain the 5th generation F-35.

According to reporting, a new F-15X will cost nearly $100 million to acquire in the 2020 budget. In 2020, the F-35A is estimated to cost $80 million. As Bloomberg recently reported the initial cost for 8 F-15X aircraft would be $1.2 billion. For that same price, the Air Force could acquire 15 of the significantly more capable F-35As.

From a unit cost perspective, there is no debate – the F-35 is by far the more affordable option, by nearly $20 million.

If I had it my way, the F-15 would fly forever, and so would I. However, the cold, hard REALITY is that time marches on, and the F-15’s mission as the front-line fighter is complete, and my fighter flying days are over! The United States leaders must develop budgets for America’s future fighter fleets that look to the future, and not be lured into investing in a 47-year-old aircraft that is more costly and less capable.

Instead, to ensure our military and USAF maintains its air superiority against any threat, not just today but for decades to come, tactical air power investments must be prioritized to the programs that will survive and deliver lethality in any future conflict.

Rather than clinging to Cold War era platforms that are quickly being outpaced by the enemy, the USAF must stay the course to prioritize the acquisition and modernization of the 5th generation F-35 fleet, focus on operational readiness and invest in next-generation air dominance technology— we must not deviate from investing in 5th generation fighters. Our future, our country’s future, and our warfighter’s success and survival depend on it.

General William R. Looney III (USAF Ret.) served 40 years in the United States Air Force and retired as a 4 Star General. During his career, he commanded an F-15 squadron, 2 F-15 fighter wings, and an Air Expeditionary Force (AEF) in Southwest Asia in addition to numerous other command tours.

This first appeared in RealClearDefense here.