A third of the Russian air force's RSK MiG-29 fighters have been rendered non-flightworthy, due to corrosion found during ongoing safety inspections.
Russia's defence ministry says 190 aircraft from its air force inventory of 291 MiG-29s had been checked for corrosion by mid-March, with 91 found to be in need of repair.
The fleet-wide inspection was initiated following two crashes in October and December 2008 involving MiG-29s assigned to the 120th Fighter Regiment in the Chita region. Inspection of both wrecks revealed extensive corrosion to the attachment points between the aircraft's fuselage and vertical empennage and the entire fleet was temporarily grounded.
Inspections of the remaining 100 aircraft by a joint defence ministry and RSK MiG commission will be carried out "according to plan", the air force says, and the former's 13th Scientific Research Institute will by late March present a report on the full findings of both crash investigations and the status of the remaining aircraft.
It is unclear at this point whether grounded aircraft will require new empennage structures, or if remedial work could be limited only to the affected attachment points.
Possible contributory factors to the corrosion issue include the poor and simplified maintenance that Russian air force MiGs received in the 1990s and early 2000s, and the widespread use of aggressive fluids for anti-icing and to prevent the build-up of ice.
Defence ministry experts say the corrosion is unlikely to be an issue for exported MiG-29s, because Russian operating conditions are more severe than those found in most other operating nations. An Indian air force inspection of more than 70 MiG-29s has already cleared the fleet of any corrosion issue, they add.