Baku to Tehran and return. The first flight was a pretty old ATR-72 which looked quite scary from outside. Inside was not bad and relatively comfortable. The flight was pleasant and on time service on board was correct. The return leg was very unpleasant. The flight was supposed to leave at 2:20 am but due to the late arrival of the aircraft from Baku it was delayed of 1hr. Then when the moment to board came we didn't have any news and the Azerbaijan Airlines ground staff disappeared. Just after 1 more hour a staff member was found by the other passenger and was obliged to give a public statement just in Farsi announcing that due to heavy fog in Baku the plane was delayed without indicating the exact departure time. As I'm Italian I could just get this information from another fellow passenger who translated to me. At 7am the mob almost attacked an Azerbaijan Airlines staff member and obliged him to give some news : he made a phone call and after 10 minutes the we suddenly started to board. Finally we left at 8pm and the flight with an A319 went fairly well. Bad weather is a standard inconvenience and flying with fog is not safe but the behaviour of Azerbaijan Airlines was simply not acceptable. We were all left for hours without any information any drink and any apologize.