F-16 fighter jets have proved highly effective in countering the jet-powered drones Russia launches at Ukraine daily. But more than half of Ukraine’s F-16s currently need to be restored to service, while maintenance work in Belgium is running behind schedule, according to a Wall Street Journal editorial dated Sept. 29.

Axar.az reports, citing The New Voice of Ukraine, that Ukrainian F-16 pilots have already shot down about 2,500 Russian drones of all types and about 650 cruise missiles, the newspaper reported. After 300 flight hours, however, the aircraft require a so-called phase inspection to keep their engines, avionics, hydraulics and other systems operational.

Ukraine relies on Western assistance for this work. The United States signed a contract worth more than $230 million with Belgian company Sabena Aerospace Engineering to maintain Ukraine’s F-16s, although subcontractors perform some of the work.

The phase inspections typically take two to six weeks in the United States but can take as long as 40 weeks in Belgium.

More than half of Ukraine’s F-16s are currently in maintenance limbo, a source told the WSJ. If the aircraft continue to be used at the same high rate and maintenance does not accelerate, Ukraine could run out of available F-16s by the end of 2026.

The Ukrainian Air Force declined to comment on the matter, the WSJ reported.