How do I get from Tisno to Zadar airport for a 6 AM flight?

It seems unlikely that you'll able to do it by bus. The night buses are seasonal only, and the only source of info I can find for night time buses is BusCroatia.

They indicate that you'd likely have to go by taxi from Tisno to either Vodice or Pirovac, and then catch the route from Vodice to Zadar that passes through Pirovac.

You want to check in an hour before, meaning you need to be at the airport at 5 at the latest, and it'll take 30 min from Zadar town (conservative estimate). So you want to arrive by 4.30am at the latest.

You say the festival ends at 2, so that's a fairly narrow window, given the bus takes 1 hour and 1 minutes to go from Vodice to Zadar.

The list of night routes that I can find indicates that there are buses leaving Vodice at 1.16am, and 6.50am. Obviously the latter is too late, meaning if you really want to take a bus, you're going to want to leave the festival in a taxi to get TO Vodice (14.5km or 16 minutes by car) before 1am, to ensure you catch the bus on time.

So realistically, you have the following options :

• pay up for a taxi for yourself to Zadar airport
• find others to share a taxi with
• miss the last hour of the festival and hope your connections (Taxi, bus, taxi) all work out
• wing it, and hope that when you're in Tisno you'll find a special bus or shuttle that's being put on just for the festival (it happens sometimes!) and therefore won't be online.
• change your flight to the next day, removing all stress from this.

enjoy it!