reported Wednesday that more than half of Ukraine’s F-16s are currently in what a Western source described as “maintenance limbo.”The same source told the newspaper that, at the current rate of operations and maintenance, Ukraine could exhaust the remainder of its available aircraft by the end of the year.

The Ukrainian Air Force declined to provide the with figures on the status of the fleet. Open-source analysis suggests that Ukraine may have received around 40-50 F-16s so far. However, a proportion of these are held back for training elsewhere in Europe, while there have been five confirmed losses. Approximately 110 F-16s have now been promised by a coalition comprising Belgium, Denmark, the Netherlands, and Norway.

The report follows ’s recent reporting on a separate constraint affecting the F-16 force: Ukraine is struggling to maintain adequate stocks of air-to-air missiles for its fighters. AIM-9 Sidewinders and AIM-120 Advanced Medium-Range Air-to-Air Missiles (AMRAAM) have been heavily used against Russian cruise missiles and drones, and Ukrainian F-16 pilots have reportedly had to ration their missile shots. Aircraft have increasingly had to rely on their internal 20mm cannon when suitable missiles are not available. This is a far from ideal substitute, as you can read about here, but Kyiv is reportedly now negotiating for tens of thousands of additional rounds of 20mm ammunition.

Ukrainian F-16s have apparently been carrying laser-guided 70mm Advanced Precision Kill Weapon System II rockets, which should provide an extremely valuable, lower-cost option for engaging long-range drones and subsonic cruise missiles. The exact status of this weapon in Ukrainian hands is unclear, but there is so far limited evidence of extensive use by its F-16s, at least in the public domain.

All these problems are closely related because the same high operational tempo that is consuming Ukraine’s missile stocks is also putting additional hours on the already well-worn F-16 airframes.

The aircraft have become a critical important component of Ukraine’s air-defense effort, particularly as Russia has expanded its use of increasingly sophisticated one-way attack drones, as we wrote about only yesterday. reports that Russia has launched around 2,000 jet-powered drones against Ukraine this month, compared with approximately 350 in June. The newer, jet-powered drones can reportedly reach speeds of up to 375 miles per hour, making them more difficult for Ukraine’s interceptor drones to engage and increasing the importance of conventional fighters. At the same time, the stocks of effectors for ground-based air defense systems are being reduced, in some cases to a critical level, increasing the reliance on crewed fighters to take up the slack.

F-16s are well-suited to the counter-drone and counter-cruise missile mission, but using them extensively against large numbers of relatively inexpensive targets presents a difficult sustainment problem. In fact, the lower speed and altitude differential between the F-16 and a jet-powered drone, compared to a propeller-driven one, makes the higher-performance weapon an target for the crewed fighter in most scenarios.

However, every sortie adds flight hours to the aircraft, while each missile engagement draws from an inventory that Ukraine and its Western partners have to replenish. As the aircraft accumulate hours, they reach scheduled inspection and maintenance intervals, increasing demand on a maintenance network that is already supporting a fleet operating under wartime conditions.

The United States has established a substantial support arrangement for that purpose. In January, the Pentagon awarded Belgian company Sabena Aerospace Engineering a contract with a ceiling of approximately $235.5 million for intermediate- and depot-level maintenance of Ukrainian F-16 aircraft and engines, together with associated material-management support. The contract runs through January 2029, with approximately $69.7 million initially obligated.

The contract provides an indication of the scale of the infrastructure required to keep the Ukrainian F-16 fleet operational. It also highlights why the reported turnaround times in Belgium are significant. A typical phase-inspection that would normally take approximately two to six weeks in the United States is reportedly taking as long as 40 weeks in Belgium.

A 40-week turnaround does not necessarily mean that an aircraft spends 40 weeks continuously undergoing a phase inspection. The overall period an aircraft is unavailable can also include waiting for parts, additional repairs, scheduling, and other work. It is unclear exactly how many Ukrainian F-16s are currently affected by these various factors.

At the same time, the reported turnaround times do point to a substantial capacity problem. Ukraine operates a relatively small F-16 fleet, so aircraft that remain unavailable for extended periods have a disproportionate effect on the number of fighters that can actually be generated for combat missions. Its mission spectrum also includes air-to-ground sorties, putting more demand on the hard-pressed F-16 fleet.

The F-16s have finite airframe lives, require increasingly substantial inspections as they accumulate hours, and depend on a supply chain for engines, components and other parts. The missiles used to destroy the targets are another finite resource. It should also be recalled that the jets supplied to Ukraine are among the oldest still in operational service. Although upgraded to F-16AM/BM standard, the airframes have accumulated a lot of hours and fatigue.

There is an additional complication with the air-to-air missile inventory, too. AMRAAM is not used only by Ukrainian F-16s, but also employed by its NASAMS ground-based air-defense systems. Sidewinders, too, have both air-launched and surface-launched applications. The same broader Western supply chain therefore has to support both fighter operations and some of Ukraine’s surface-to-air missile systems. Stocks of both AMRAAM and Sidewinder have been eroded by Ukraine, as well as by combat actions in the Middle East.

At the same time, Ukraine is continuing to receive additional F-16s. Belgium has said it will transfer three more aircraft to Ukraine before the end of this year. More aircraft will increase the potential size of the force, but they will also add to the requirement for spare parts, engines, technicians and depot capacity.

“There is an important agreement with Belgium on the transfer of three F-16 fighter jets by the end of this year,” Ukrainian President Volodymyr Zelensky wrote on X. “We will work to receive these aircraft through an accelerated procedure.”Zelensky said Ukraine had already received “urgent deliveries” of F-16 weapons from Belgium and Spain, among other countries.

The alternatives to the F-16 are also limited in the near term. Ukraine continues to operate the Soviet-era MiG-29 Fulcrum and a small number of Su-27 Flankers, but these aircraft are themselves aging and are also required for strike missions. In their favor, the Soviet types were designed around a different concept of operations, making them easier to maintain in the field, and Ukraine has its own support infrastructure to sustain them.

The French Mirage 2000-5F force provides another Western option, but deliveries have been relatively limited, and additional aircraft are arriving incrementally rather than in numbers that can quickly compensate for a major reduction in F-16 availability. The longer-term fighter replacement plan is more ambitious. Sweden has agreed to provide 16 Gripen C/D fighters, with the first aircraft expected in early 2027, while a separate agreement covers the purchase of 16 new Gripen E fighters whose deliveries are not scheduled to begin until early 2029.

That leaves the F-16 as the principal Western fighter capability available to Ukraine for the immediate future, increasing the significance of any prolonged disruption to its maintenance pipeline or its supply of air-to-air weapons. Ukraine needs enough aircraft to maintain a meaningful combat presence, enough missiles to arm them for the missions they are being asked to fly, and enough maintenance capacity to keep those aircraft available as their flight hours accumulate.

All this is becoming more important as Russia’s aerial campaign evolves. If the increase in faster jet-powered drones continues, Ukraine may have to devote still more fighter sorties to countering them at the very same time that a large portion of its existing F-16 fleet is reportedly unavailable and its stocks of air-to-air missiles are under serious pressure.