Not only do the US not allow sale of aircraft but they don't allow the sale of parts either, and at the time of the revolution in 79 when the US-sponsored Shah was overthrown Iranair (and nearly all Iranian industry) was almost entirely reliant on US and Western know-how and technicians. Iranair had to go from being an airline that had lots of American engineers and a free flow of parts to doing all their own maintenence with Iranian nationals, and having to take very circuituous routes to obtaining parts for their fleet. They managed it brilliantly and without a noticeable gap in ops. They have been politically isolated for twenty years now, and their engineering and ops depts are totally world-class and necessarily self-sufficient. Airbus have made hay at Boeing's expense (as they have in many other regions) and sold a fleet of A300-600s to the airline. Expect an order for A340s to replace the 747s.
Iranair have a good reputation for service, and their route map spans the globe, flying as far afield as China, Japan, Africa, and of course a couple of dozen cities in Europe, as well as comprehensive services across their home turf, the Middle East and the Indian subcontinent and Asia. Tehran's location means that it would be an ideal transit point for passengers travelling from Europe to Asia, and it's a shame the Iranians haven't capitalised on that. It's also a beautiful and historical country and while tourism is reasonably buoyant (although unfortunately Americans are excluded from the many national groups who travel there every year), it could be a much bigger earner for the country. I am as supportive as anyone of getting rid of foreign interference (the Shah and his paymasters in 79) but the people of Iran now want to live normally and not under religious law, and when this finally happens Iran will become a big destination and Iranair could rival Emirates or Singapore Airlines as a top quality airline with a powerful international hub. They certainly deserve it for hanging in there all these years.
fly Saha Air 707s daily from Tehran's downtown Mehrabad to Mashhad, Kish Island and Ahwaz