For months, many in Washington have been scratching their heads over the Air Force’s fiscal 2020 budget submission requesting fourth-generation F-15s — a design first flown in 1972. Ever since F-117 stealth fighters amazed the world in Operation Desert Storm, the service committed to fifth-generation fighter modernization via the F-22 and F-35. Their stealth designs and information gathering capabilities reset the rules of the air superiority mission for friend and foe alike. The scale of the development was akin to the telephone’s evolution from landlines to smart devices. Circumstances surrounding this decision became even more clouded when Secretary of the Air Force Heather Wilson explained: “Our [FY20] budget proposal that we initially submitted did not include additional fourth-generation aircraft.” To explain this decision — and perhaps to provide acting Secretary of Defense Patrick Shanahan with some top cover — officials at the Cost Assessment and Program Evaluation office, or CAPE, held a press briefing last week.

While their arguments were meant to bolster the case for buying 1960s-era designed F-15s, a deeper look reveals that the Air Force should ramp up F-35 procurement and aggressively press forward with the service’s next-generation air dominance program. The stakes in this decision are significant, for air superiority is a keystone mission in the Department of Defense — no other form of power projection is viable without it.

Press accounts reveal that CAPE focused its case on four main points: boosting Air Force combat capacity in the near term; driving down aircraft sustainment cost; additional standoff capabilities; and ensuring diversity in the fighter-aircraft industrial base.

These are important issues, but buying new F-15s is not the smartest way of accomplishing them.

CAPE is correct on the first issue — the Air Force is too small. However, in building tomorrow’s Air Force, it is crucial to acquire the right balance of capabilities. The Air Force currently has 1,753 air superiority fighters, but just 186 F-22s and approximately 175 F-35s meet modern demands in an era of peer conflict. This is an 80-20 percentage split between fourth- and fifth-generation fighters — a troubling reality given that strategic imperatives, the threat environment and the National Defense Strategy demand cutting-edge, survivable capabilities. Concurrent global demand, force rotation factors and the sheer scale of regions like the Pacific mean that just a handful of F-22s and F-35s would be available at any time and place. Combat operations are not viable for the long haul if airmen cannot execute their missions successfully and get home safe. That is a recipe for disaster that could see ships at sea, soldiers on the ground, space and cyber facilities, regional bases, and support aircraft at risk.

Addressing this shortfall demands boosting F-35 acquisition to at least 72 aircraft per year, not bolstering a fourth-generation inventory that is already too large from a proportional vantage.

Regarding F-35 sustainment costs, they are coming down rapidly. F-15 and F-35 rates are set to intersect soon in the $25,000-$30,000 per flying hour range. It is also important to consider that it takes far more F-15s to accomplish a mission that a single F-35 can achieve, with the latter at far less risk.

This is not a new trend. In Desert Storm, it took roughly 19 non-stealthy aircraft to do what a single stealthy F-117 could accomplish. One F-35 pilot recently explained: “Five to eight years ago, we would plan an entire force package of [fourth-generation] aircraft, about 20-30 aircraft, all to maybe have a slim hope of taking down a modern surface-to-air threat — just one. Now, we train to accomplish the same mission with far greater certainty using just a few F-35s, while continuing to execute a host of other tasks.” Mission costs matter, and by this measure the F-35 is a far more prudent choice.

As for standoff weapons, while they afford commanders with valuable options, the Air Force has no shortage of standoff weapons carriers. They need more stand-in airplanes. The entire legacy fighter force of over 1,000 aircraft, along with B-1 and B-52s, can carry standoff munitions. Nor are more modern types like the B-2, B-21, F-22, and F-35 precluded from employing these weapons. There is also a basic monetary consideration when balancing stand-in and standoff capabilities. The latter is far more expensive on a per unit cost — in excess of $1 million a missile versus thousands of dollars for an air dropped munition. A theater-level air campaign involves upward of 40,000 aim points — do the math. Nor are many of these standoff munitions stealthy. They stand a high risk of being shot down.

CAPE is rightly concerned about the industrial base. Since the end of the Cold War, the nation has seen a diverse base of manufacturers consolidate into a few companies. However, there is a difference between sustaining legacy assembly lines and investing in forward-leaning design expertise. The latter is a far more difficult competency to cultivate and has little relation to producing additive copies of a mature design. Honing this talent demands harnessing new technologies and cutting-edge concepts of operation to meet tomorrow’s air superiority challenge. Committing resources to the next-generation air dominance program — concepts like Kratos’ XQ-58 Valkyrie uninhabited loyal wingman and Boeing’s manned-unmanned Airpower Teaming System — are all right steps in this direction. The B-21 also presents tremendous value, with long-range strike missions able to eliminate adversary air targets. Procuring more F-15s crowds out funding from these essential efforts.

Congress needs to take these points into consideration as it assesses the best air superiority path forward.

CAPE is right to be concerned, however. Their prescribed solution is far off the mark and risks exacerbating the problems they are trying to address. In fact, the FY20 budget submission sees F-35 acquisition numbers reduced by a squadron’s worth over the Future Year’s Defense Program versus plans outlined in the FY19 FYDP.

The near-term air superiority gap is best met by boosting F-35 production, while the longer-range challenge demands new programs and fresh thinking. Airmen are charged with the mission of flying, fighting and winning. We had better equip them appropriately.

Douglas Birkey is the executive director for aerospace studies at the Mitchell Institute, where he researches issues relating to the future of aerospace and national security.