In Britain, a British businessman was sentenced to 30 months in prison for illegally exporting F-4 and MiG aircraft parts to Iran from 2010 to 2016. The smuggler (Alexander George) used several cutouts (third parties who often did not know what they actually shipping and what the final destination would be). One cutout would buy the parts from American suppliers and others who ship them to various companies in the Middle East and Asia before they eventually ended up in Iran. The cutouts cooperated with British investigators and received suspended sentences. Alexander George received at least $6.3 million for these transactions, which are just a small part of a global network of smugglers Iran uses to obtain replacement parts for its air force. These smugglers are numerous and often caught. Prosecutions in the United States and Europe occur regularly and these are usually uncovered while the smugglers are still at it. There are apparently many smugglers who did it for a while then quietly withdrew from the business.
Overall this aircraft parts smuggling obtains up to $100 million worth of parts in some years. Many are actually well-made counterfeits from China or Russia but Iranian agents are always seeking original parts from countries that still have (or recently retired) F-4 or F-5 aircraft. Since the 1990s most remaining users of these aircraft have retired them. Since all these users are outside the United States it is difficult for the Americans to ensure the retired aircraft are not scrapped. Iran has agents (usually local opportunists and not ethnic Iranians) everywhere who know that Iran is willing to turn scrap into gold and the methods of concealing the shipments are widely known because these techniques (using cutouts and, where possible, bribes to obtain false documents) are methods long used to move all sorts of contraband.
Yet for all this effort (over three decades and at a cost of over a billion dollars), Iran has not got a lot to show for it. Iranian military leaders admit that their air force, despite remarkable efforts to improvise, is in sad shape. Iran currently has about two hundred fighters and fighter-bombers that are flyable but most of these are good for only about one sortie a day. All of these ancient aircraft are subject to breakdowns that can keep them on the ground for days or weeks. The chronic shortage of spare parts limits the number of hours the aircraft can be flown. This means pilots lack good flying skills. The poor maintenance and untrained pilots leads to more accidents.
Iran has about fifty modern fighters capable of flying and fighting. Half of these are American F-14s from the 1970s. Although frequently refurbished none have been upgraded much although Iran claims two F-14s have received some modern equipment. Iran has about 30 flyable MiG-29s, all built in the late 1980s and none have received the upgrades most other MiG-29s of that period have received.
Russia helped supply components to keep most of the 36 MiG-29s Iran received (in the late 1980s through 1991) flying. The only notable upgrade was to enable these aircraft to use Iranian made anti-ship missiles. With Chinese help, Iran has kept about fifty of its 1960s vintage F-4 fighter-bombers operational, but as reconnaissance aircraft and bombers. Iran has about fifty of its nearly fifty year old F-5 fighter-bombers flyable. These, like the F-4s, are considered dangerous to fly given their age and improvised maintenance and repairs over the years. The pilots don’t get a lot of time in the air and are this much less capable than the Arab fighter pilots they face, who have modern, well maintained Western warplanes that are regularly upgraded and flown a lot. Iran also has about 60 elderly Russian ground attack aircraft; mainly Su-24s and Su-22s plus a few Su-25s. Iran has tried to create “new” aircraft by heavily modifying F-5s but this has not produced any significant results other than ten aircraft that are flyable but not very capable.
Iran obtained new aircraft in some strange and dramatic ways. One unforeseen opportunity was the 1991 Gulf War. Many Iraqi aircraft (most of them Russian-built) fled to Iran to avoid the American attack. The Iranians never returned them. Iran ended up with up to 60 MiG-29s. There were also 18 Su-24s, a force that was expanded by more purchases from Russia. Black market spare parts have been available, but the MiG-29 is a notoriously difficult aircraft to maintain, even when you have all the parts you need.
After arch-enemy Saddam Hussein was overthrown in 2003 (by a U.S.-British invasion) Iran felt free to concentrate on refurbishing more of its elderly warplanes. With more money and manpower diverted to this program a lot of the older aircraft were made operational once more. In 2013 Iran announced that ground crews and other technical personnel at an air force base had spent 45,000 manhours to get two Mirage F1 fighters back into flying condition. Iran received 24 of these aircraft from Iraq in 1991, when Saddam ordered most of his combat aircraft to fly to Iran and surrender (rather than be bombed by coalition aircraft). Iran kept all these aircraft but found it difficult to operate them, especially if none were already in the Iranian Air Force. The aircraft did not come with any support or maintenance equipment and especially no spare parts. Over the years, some parts and maintenance equipment were obtained, but in two decades these older aircraft, left outside most of that time, deteriorated. The two Mirages restored did not remain flyable for long. That made it clear that many of these refurbs just were not the effort. Meanwhile, China proved willing and able to supply some parts and electronics that could be used in the American warplanes.
Refurbishing older warplanes meant taking them apart, obtaining (via China, smugglers or local manufacture) new or used parts, replacing the defective ones and then reassembling it all. The two refurbished Mirage F1s managed to fly, but since then little has been heard or seen of them. This sort of thing seems like a useful way to keep ground crews busy when the air force can’t get enough money to let even the flyable aircraft fly much. Fuel and spares cost money, money that Iran does not have. Earlier news stories have mentioned similar refurbishing projects for F-14s, F-5s, F-4s, and MiG-29s which have been more successful, up to a point.
The Iranian problem is that three decades of sanctions have made it impossible to replace obsolete and worn out gear or even maintain the elderly systems they have to rely on. For example, Iran has been having increasing problems keeping its 1970s era F-5s operational. The ones that are still flying tend to crash a lot or not be available for use because of maintenance problems (including spare parts shortages). Spare parts for all U.S. aircraft Iran still uses have been hard to come by. Iran has managed, sort of. Nevertheless, the Iranian Air Force is largely a fraud. It has lots of aircraft that, for the most part, sit there but can't fly because of age and lack of replacement parts. Those that can fly would likely provide target practice for enemy fighters.
The Iranian Air Force is still recovering from the effects of the 1979 revolution, which led to an embargo on spare parts and new aircraft. Despite that, many Iranian warplanes remain flyable but only for short periods. The main reason for even that is an extensive smuggling operation that obtains spare parts. Two of their aircraft, the U.S. F-4D and F-5E Tiger, were widely used around the world. Somewhere, someone had parts for these planes that Iran could buy. That was the main reason so many of these are still flying for the Iranian air force, although only about half of those declared flyable are capable of doing so at any time. This was less the case with Iran's most expensive warplane, the U.S. F-14 Tomcat. Iran was the only export customer of this aircraft. Some F-14s have been kept flyable, despite the rumored sabotage of Iran's AIM-54 Phoenix missiles by U.S. technicians as they were leaving. To demonstrate this, they sent 25 F-14s on a fly-over of Tehran in 1985. Today, Iran can still put at least 20 F-14s into the air on short notice. The manhours spent on keeping these aircraft flyable is far greater than any other user had to devote to that. Iranian pilots are not very experienced but their aircraft maintainers are, which would be an asset if Iran could obtain modern aircraft.
Despite all the smuggling and improvisation, Iran is stuck with the oldest, least capable fleet of warplanes in the Middle East. The lifting of most sanctions in 2015 has not changed the situation much and in 2018 the American revived their sanctions because more evidence of Iran cheating on the 2015 agreement were uncovered. No wonder Iran has put so much effort into building ballistic missiles and, eventually, nuclear weapons. In many ways building these weapons is simpler than buying and maintaining modern combat aircraft. Nukes and ballistic missiles require less maintenance because they are used only once. But you can show off the warplanes regularly and that still counts for something.