What is the cheapest method from venice to the airport? And how long would it take? Our flight leaves at 0955.
Cheapest way would be to walk to Piazzale Roma and take the bus from there. Next cheapest is vaporetto to Piazzale Roma and bus from there. How long that takes depends on where your hotel is (which vaporetto stop).
The bus from Piazzale Roma takes 33 minutes (it makes a few stops) and goes every 15 minutes starting at 7:10 weekdays, before that every half hour starting at 5:40. Saturday, Sunday, and holidays every 20 minutes starting at 6:40 and every half hour before that. The cost is 6 euro. Validate your ticket on the bus in the stamping machine or the chip reader. So if you want to be at the airport 2 hours before your flight, the 7:25 bus should do it.
If you're going to buy a vaporetto pass, you can buy a one-way upgrade at the same time for the bus from Piazzale Roma to the airport. Then I think it only costs an additional 4 euros.