 Following the Russian annexation of Crimea and subsequent War in Donbass in 2014, Ukraine increased its military budget, allowing stored Su-27s to be returned to service.The in Zaporizhia began modernizing the Su-27 to NATO standards in 2012, which involved a minor overhaul of the radar, navigation and communication equipment.Aircraft with this modification are designated Su-27P1M and Su-27UB1M.