Ukraine is flying its American-made F-16 fighter jets so frequently to intercept Russian jet-powered drones that maintenance demands are threatening to keep a significant portion of the fleet out of service. Ukrainian President Volodymyr Zelenskyy has said that roughly half of the country’s F-16s, or about 25 aircraft, are grounded for maintenance or undergoing repairs in Europe.

In an October 1 interview with the Financial Times, Zelenskyy said many of Ukraine’s F-16s spend extended periods abroad for repairs and maintenance, limiting the number available for combat missions. Kyiv is pressing Western allies to move more maintenance operations into Ukraine so damaged aircraft can return to service more quickly.

The United States has awarded Belgium-based Sabena Aerospace Engineering a contract worth up to $235.5 million to support maintenance of Ukraine’s F-16 fleet. The effort comes as Ukraine faces growing demands on its air defenses amid continued Russian attacks.

Ukraine’s Foreign Ministry has pushed back against claims that the fleet’s readiness has collapsed. Spokesman Georgiy Tykhy disputed a Wall Street Journal report that more than half of the aircraft were grounded, while acknowledging that parts for older F-16 models are increasingly difficult to obtain because some are no longer manufactured.

Ukraine is also seeking additional aircraft and ammunition from its European partners. During meetings last week, Zelenskyy asked Belgian King Philippe and Prime Minister Bart De Wever for more F-16s as Russia continued striking Ukrainian energy infrastructure.

De Wever said Belgium would deliver 10 F-16s to Ukraine by the end of the year, an increase from the three aircraft Zelenskyy had announced on September 29. The Belgian prime minister announced after meeting Zelenskyy on the sidelines of the October 15 European Union summit in Brussels.

Belgium originally pledged 30 F-16s to Ukraine in May 2024, with transfers scheduled to continue through 2028. Deliveries had been delayed because Belgium lacked sufficient U.S.-made F-35 fighters to replace its aging fleet. De Wever has said that the replacement aircraft are now beginning to arrive.

The pressure on Ukraine’s fighter fleet reflects the challenge of using a limited number of combat aircraft to perform air-defense missions day after day. Retired Air Force Lt. Gen. David A. Deptula, head of the Washington-area Mitchell Institute for Aerospace Studies, said Ukraine has been “forced to use a relatively small fighter fleet day after day as a substitute for an adequately resourced, layered air defense system.”

That approach risks wearing out aircraft faster than they can be maintained or replaced. Deptula warned that Ukraine was “consuming a finite resource faster than they should,” adding, “It's not a sustainable long-term proposition.”

Despite the strain, Ukraine’s F-16s have played an important role in countering Russian aerial attacks. Ukrainian Air Force spokesman Col. Yurii Ihnat said the aircraft accounted for “a significant portion” of the 1,900 jet-powered drones intercepted during the previous month, out of 3,500 launched by Russia.

The figures underscore both the effectiveness of Ukraine’s fighter operations and the challenge of sustaining them. With aircraft awaiting repairs and additional deliveries still needed, Kyiv is seeking faster maintenance support, more ammunition, and reinforcements from Western allies to keep its air defenses operating.