Airports announced as int'l airports such as Tehran (Mehrabad), Shiraz, Payam, Tabriz, B.Abbas are considered as transit airports which can handle aircraft to aircraft transshipments. All such airports enjoy equipment as well as supervisory bodies attendance.
Useful link : www.iricao.org
Apart from Iran Air (Homa) and some other local carriers, many Int'l carriers call Iranian airports by passenger & cargo flights.
Useful link :www.iranair.com
Iran is a member country of ICAO, IATA, and a party to warshawa & Montreal conventions and protocols. The national law for transit operations through Iran, where applicable, should also be observed.