The Air Force's newest fighter jet may not be what it needs to win the next war

• In March, the Air Force accepted the first F-15EX, the first new fourth-generation fighter in 20 years.
• The F-15EX is based on a proven design and will replace jets that are close to their breaking points.
• But critics say that in the wars of the future, a jet like the F-15EX is just "an expensive target."

In March, the Air Force accepted its newest fighter, the F-15EX, the first new fourth-generation fighter in over two decades.

At a ceremony to mark the occasion, Air National Guard Director Lt. Gen. Mike Loh said the fighter's arrival "is very timely," as the Air Force "must ensure that we have the most capable combat aircraft defending our shores during this time of great-power competition."

The Air Force hopes to acquire 144 of the jets over the next decade and has an option to buy up to 200. Despite the fanfare, the decision to acquire the F-15EX has faced considerable criticism.

"It's an expensive way of getting shot down, and the Air Force is wholly ill-equipped to field this aircraft from multiple standpoints," Doug Birkey, the executive director of the Mitchell Institute for Aerospace Power Studies, told Insider.

The criticism stems from concerns that the F-15EX, a modernized version of a 45-year-old design, stands little to no chance of survival in the modern threat environment, that it will take resources from other designs and programs, and that it will actually cost more in the long run than more fifth-generation jets.

Replacing aging fighters

At first glance, buying the F-15EX seems like a no-brainer. It is a modernization of a tried-and-true design that has never lost a battle in aerial combat.

Moreover, the aging F-15Cs and F-15Ds it will replace are close to their breaking points, with 75% of them flying "well beyond" their service life, according to Lt. Gen. Duke Richardson, military deputy for the Office of the Assistant Secretary of the Air Force for Acquisition, Technology, and Logistics.

Those fighters were supposed to be replaced by the F-22 Raptor, a fifth-generation fighter, but F-22 production ceased in 2009 with less than half the original order built due to budget cuts.

That production halt, and the slow rollout and ballooning cost of the F-35, also a fifth-generation fighter, have forced the Air Force to use F-15s past their expected service lives.

Although the F-15EX's per-unit cost of $87.7 million is slightly more than the F-35's $77.9 million, the F-15EX's operating cost of $27,000 an hour is expected to be lower than that of the F-35, which Lockheed Martin says is $36,000. (The F-35's per-hour cost has come down in recent years, and Lockheed says it could be reduced to $25,000 by 2025.)

The Air Force wants a mix of fourth- and fifth-generation aircraft, as not all fighter jets will have the same missions and thus do not need the same capabilities.

The Defense Department also wants to maintain a "robust industrial base." Without the F-15, all of the Air Force's fighters would be built by Lockheed Martin.

Questionable survivability and cost

The F-15EX's lack of stealth capabilities is a significant tradeoff.

Non-stealth aircraft are heavily reliant on accompanying support aircraft - doing things like electronic warfare, combat escort, and air-defense suppression - to carry out their missions. This dramatically increases the number of jets need to carry out airstrikes.

In one operation during Desert Storm, for instance, three targets at one airfield in Iraq required 41 US and Saudi fourth-generation aircraft to ensure a successful strike - only eight of those aircraft actually dropped bombs.

Around the same time, 20 F-117s, the US's first stealth aircraft, operating on their own successfully attacked 38 sites at 28 separate target areas.

More aircraft naturally mean higher costs, and many of those support aircraft are no longer in the Air Force's inventory, which means it has to rely on the Navy to provide them.

Moreover, Russian and Chinese surface-to-air missile systems (SAMs) and air-to-air missiles (AAMs) have gotten considerably more sophisticated since the 1990s.

China has a number of AAMs in service and in development that are just as capable as the US's AAMs, and some even have longer ranges. Iran has already bought advanced anti-air weaponry from Russia and may buy more.

"It's not just fighting China and Russia. It's wherever their stuff happens to be," Birkey said, pointing to Syria as an example.

Those factors all raise questions about F-15EX's survivability and cost benefits.

"The problem is, if they are not good enough to do the job, survive, and keep rolling, what did you buy?" Birkey said. "You bought an expensive target."

A more threatening environment

If the F-15EX were to go up against such weaponry and losses were to mount, replacing them would not be easy.

"We no longer live in the era where we can back all these kinds of losses," Birkey told Insider.

"We don't have the aircraft-production capabilities and capacity, and we certainly don't have the pilot-generation capabilities," Birkey said, adding that the service already has a pilot shortage "and none of our guys are dying due to combat loss."

While the F-35EX's lack of stealth is a big problem, critics don't suggest only buying F-35s or F-22s.

Rather, many say the Air Force should double-down on new designs and concepts, like the Next Generation Air Dominance program or unmanned fighters like Kratos Defense's XQ-58A Valkyrie or Boeing's Airpower Teaming System.

With budgets already tight, more money spent on the F-15EX may mean less for those programs.

US defense officials acknowledge that a great-power war would be far different from the conflicts the US has fought over the past 20 years.

In April, during his first significant policy speech, Secretary of Defense Lloyd Austin said "the way we fight the next major war is going to look very different from the way we fought the last ones" and emphasized a need for "the right mix of technology, operational concepts and capabilities."

Gen. Charles Q. Brown, the Air Force chief of staff, admitted in his first major strategic document that in a future war, the Air Force could face combat losses "more akin to the World War II era" than to recent conflicts.

Fifth-generation jets are designed with this in mind and are made to win conflicts with stakes beyond the battlefield, Birkey told Insider.

"You could fight in Iraq and Afghanistan for two decades, effectively lose in both, and nothing really changes in mainstream America," Birkey said.

"The wars that we're increasingly looking at, and for which the F-22 and F-35 are built, are wars where if we do not succeed, life fundamentally changes in a very bad way," he added. "We need to wake up to that and act accordingly."