The Ukrainian Air Force inherited about 66-70 Su-27 aircraft after the collapse of the Soviet Union. Lack of funds in addition to the Su-27's high maintenance led to a shortage of spare parts and inadequate servicing, resulting in approximately 34 remaining in service as of 2019. Years of underfunding meant that the air force has not received a new Su-27 since 1991. Between 2007 and 2017, as many as 65 combat jets were sold abroad, including nine Su-27s. In 2009, amid declining relations with Russia, the Ukrainian Air Force began to have difficulty obtaining spare parts from Sukhoi. Only 19 Su-27s were serviceable at the time of the Russian annexation of Crimea and subsequent War in Donbass in 2014. Following the Russian invasion, Ukraine increased its military budget, allowing stored Su-27s to be returned to service.