Keeping top combat aircraft flying is expected to only get more expensive

• Sustainment costs for complex aircraft like the F-35 are on the rise.
• A new report analyzes what's driving these costs, as well as global military aviation trends over the next decade.
• Increased production of large drones is a notable trend, as these systems have shorter lifespans and require less sustainment.

The cost for the US and other militaries to keep newer combat aircraft ready to fly is going to soar in the coming years, a new report on sustainment trends argues.

A new report from the American consulting firm Oliver Wyman projects global military aircraft spending over the next decade, including an annual sustainment cost growth of 1.1% through 2036. That's a pace roughly 11 times faster than the previous decade.

The report forecasts a spike in deliveries of advanced fourth-generation and fifth-generation aircraft and more aircraft in active service across global militaries.

Demand for the F-35 Lightning II Joint Strike stealth fighter, in particular, is anticipated to remain strong at over 50% of the fighter market as global air forces gradually replace their aging in-service aircraft.

The US and many of its allies in Europe and Asia are building advanced F-35 fighter fleets, recognized by some officers as the bare minimum for high-level modern air combat. The US and others are also exploring new sixth-generation designs.

"Costs may stabilize in the near-term as older fleets leave service" and the cost of keeping those systems running decreases, the Oliver Wyman report says, "but US costs will continue to rise as replacement aircraft with complex/costly designs enter service in large numbers late in the decade."

The costs of sustaining high-end aircraft

The F-35 stealth fighter is the US military's most advanced aircraft in service today. The US operates around 700 of these planes with plans to acquire over 2,400 of them in total. A 2024 Government Accountability Office report put the lifetime cost of the program at $2 trillion, 44% higher than the 2018 estimate.

The increase was tied to the extension of the aircraft's anticipated service life, inflation, and rising sustainment costs. The military has tried to cut costs by reducing flight time.

Another factor affecting F-35 costs is the lingering effect of the military's concurrency problem, which saw the Pentagon rush to field the jet while development was still underway.

That decision has led to billions of dollars in added cost growth and continues to complicate sustainment today as additional work is needed to bring the older airframes up to the standards of the newer production models.

"There are some issues that are unique to the F-35, and then there are issues that transcend the F-35," Doug Berenson, an analyst at Oliver Wyman, told Business Insider, identifying insufficient depot maintenance capacity and individual systems that require more time and specific parts to fix as issues facing broader advanced aircraft.

Fielding more advanced aircraft drives up maintenance and sustainment costs because their systems are more complex — from stealth coatings and software-heavy mission systems to advanced engines and avionics. Keeping those components operational generally requires more specialized labor, tighter tolerances, and more time than maintaining older aircraft.

While the F-35 is heavily affecting sustainment spending, the B-21 Raider stealth bomber's entry into service is expected to affect the budget as well. The new F-47 will likely do the same, and the eventual maintenance costs for larger drones like the US Air Force's Collaborative Combat Aircraft, while still somewhat unclear, ought to also have an effect on sustainment costs, though in a different way than advanced crewed aircraft.

Where drones factor in

Oliver Wyman's new report projects that drone deliveries across global militaries will spike in the late 2020s and early 2030s. The report says larger, higher-end surveillance and strike drones designed to fly long distances, carry sensors or weapons, and operate alongside crewed aircraft will represent a significant share of combat aircraft inventory.

Berenson said the rising trend of drones was a stand-out takeaway because it's the most irreversible as more militaries embrace uncrewed systems.

"It's going to touch every mission and every element of the force, and it's going to upend what it means to do aircraft sustainment," he said.

The lifespans and costs of large drones vary depending on their capabilities and mission sets, but they're not nearly as exquisite as crewed combat aircraft. For example, the Air Force's plans to keep its CCAs or "loyal wingmen" operable for 10 years or less, upgrading them when needed but keeping them at a much lower cost. Many are seen as expendable assets.

The Oliver Wyman aircraft sustainment report said that "these aircraft will be designed for a much shorter service life than crewed aircraft, minimizing requirements for depot maintenance, spare parts, and other services."