It is preferable to arrive at the airport better a little earlier than too late.
We calculate the required time as follows:
1. Required time for the transfer to airport
2. Check-In time (2 hours)
3. Safety time (1 hour) in case of traffic jam, highway accident or bad weather conditions.
So for Zurich airport we will leave from St Anton 5 hours before takeoff. For Innsbruck 3 hours before take-off.