Domestic air fares in Iran are low and flights on most routes are frequent. For possibilities, check out www.parvazyab.com, though you'll need your best Farsi.
Iran Air is the largest among a growing roster of domestic airlines and boasts an extensive network of flights, covering most provincial capitals. Domestic prices are set by the government, so it doesn’t matter which airline you fly, the price will be the same. For tickets it’s best to use one of the many travel agencies, where you’ll get all the options, rather than an airline office.
Iran’s domestic airlines:
When making a booking, check the aircraft type and avoid any clunking old Tupolevs that have yet to fall out of Iran’s skies. Mahan Air, Iran Air and Iran Aseman are the most reliable and have the most routes. Whichever airline you choose you’ll find delays are common. Despite this, get to the airport at least an hour ahead of domestic departures.
Getting a domestic ticket from outside Iran is difficult. Sanctions mean paying for a seat online (if online booking is available) doesn’t work. It is theoretically possible to call an Iran Air office outside Iran and get a booking reference, which you then pay for at an Iran Air office in Iran or at Mehrabad Airport in Tehran. More reliably, use any Iranian-based tour agency.