I’m planning to fly a few weeks from now into Tehran Imam Khomeini International Airport; arrival time is scheduled at 4am. I’d then like to fly the very same morning to Shiraz. Is it possible to purchase an Iranian internal flight from overseas? How much should I pay for a taxi ride from Tehran Imam Khomeini International Airport to Mehrabad Airport?
Usually by purchasing your international tickets, you will be offered a free-of-charge domestic flight, just ask your travel agent for more information.
For booking your flight ticket you can check: Iran flight ticket booking.
A taxi between the IKA and THR usually costs about $15, but there is a bus which leaves IKA for THR every hour.
For your transfers you can check: http://www.iranairporttransfer.com