In 1970s, Iran was an ally of the USA and the “shah” Pahlavi tend to buy anything which can fly from the USA. President Nixon and his security adviser Kissenger visited Tehran and Washington was not disturbed to sell F-14s to Iran. Shah singed an agreement for 80 F-14s. After the revolution in 1979, everything has changed. Iran became a hostile for the USA. In the leaderhip of the USA, an extended sanction imposed to the Islamic Iran by the “west”. This was a big disadvantage for the aircrafts logistic.
The army’s requirements had to be met. So, facts make Iran a market for Russia. Iran bought Russian aircrafts but sustaining different types of aircraft inventory is not so easy. Iran has lost half of its F-14s which are the only 4th generation aircrafts in Iran inventory with the Mig-29s. Moreover, most of the aircraft inventory was 3rd generation aircrafts which were F-4s and F-5s. After 40 years, American aircrafts in Iran inventory needs replacement more than modernization.
In 2014, Iran and Russia agreed to deal for 48 Su-30s. The delivery is planning to begin in 2018 and Iran will pay $50m per each. On the other hand, all military contracts have to be confirmed by Ayatollah Sayyed Ali Hosseini Khamenei and he has not signed Su-30s agreement yet.
After a long strangulation, by the agrement with the USA, all restrictions on weapons-sales to Iran are on schedule to end in 2021. Iran has a chance to modernize its military power and it would be wise to start with the Air Force. If Iran Air Force will enlarge its weapons capability, the cards will be dealt again in the region. However, we have to wait for the result of the “match” between the USA, Russia, and Islamic Revalutionary Guards which will be finished by Ayatollah Khamenei.