Probably best to fly into Casa and take the train into Fez. AUI has a pick-up service from the Fez train station, and airport. If you can get a flight into Fez, power to you but hops to Fez from the airport you are likely to fly into will take unnecessary time/money.
Once your here, when you travel on the weekends, you can find cheap flights via RyanAir if your visiting Europe at all. If you’re going anywhere East, check out Russian Airlines (such as S7).