Some Bulgarian air force pilots have refused to fly their Soviet-built MiG-29 jets in planned training exercises, citing safety concerns with the outdated aircraft.
"Some of the pilots from Graf Ignatievo air base will not perform training flights because of insecurity," Bulgarian Deputy Defense Minister Atanas Zapryanov said on October 24.
The pilots have also cited concerns about poor preparedness due to a lack of flying hours, Zapryanov said, but he insisted that the jets are fully airworthy.
Bulgaria joined NATO in 2004, but much of its military equipment is still Russian-made. Out of a fleet of 16, Bulgaria's air force currently has just seven aging MiG-29 aircraft in good flying order.
The Balkan country has launched a 770-million-euro tender to replace them with eight new fighter jets.
Prime Minister Boyko Borisov's conservative government has been fighting President Rumen Radev - a former fighter pilot - and opposition Socialists since May over the purchase of the new aircraft.
At one point, an interim government appointed by Radev decided that Bulgaria would buy Swedish-made Gripen jets. But a parliamentary committee in June vetoed that, and instead asked for proposals to buy Portugal's secondhand U.S. F-16 jets and Eurofighter Typhoons.
Defense Minister Krasimir Karakadzhanow accused the boycotting pilots of starting a politically-motivated campaign. He insisted that Bulgaria will renovate all its MiG-29s and about 20 Russian-made Su-25 bombers.
The ministry recently received four new MiG-29 engines and six used ones in a deal with Russia, but problems with documentation have delayed their use.
As a NATO member, Bulgaria has an obligation to keep at least one squadron of 12 planes in good fighting order.
Since February 2016, the country's inability to do so has forced the parliament to authorize NATO to help protect its air space.
Based on reporting by dpa and AFP