Advice on Early Morning Departure from Venice

I doubt if it is an international flight. It is most likely a domestic flight to another city to catch the international flight. Therefore one and a half to two hours is more than adequate. So that should help.

The Marco Polo Airport opens at 4:45 a.m. The earliest ATVO bus departs the Piazzale Roma at 4:20 a.m.

The earliest the Alilaguana Orange line begins at San Marco is 5:58am, arriving at the airport at 7:12am - too late for you.

http://www.alilaguna.it/images/stories/linee/mappe/linea_arancio_2016_17.pdf

Want to add that I've taken a flight from Venice (direct ) to Philadelphia, departing ~11:30 a.m., did allow three hours, but didn't really need nearly that much.

We had an early flight too, can't remember the time, but our vrbo host set up a taxi for us. A little pricey but picked us right up and whisked us to the airport! Fun too!

Kim

Several years ago I had a early 7:00 AM departure from VCE. It was an international flight to CDG then SEA. Travel agent for our group put us up the night before in some obscure business hotel outside of the car free zone where we could get 4:30 AM taxi pickups at the hotel for transportation to VCE. For some reason, the hotel could or would not order taxis in advance. There apparently are a lot of 7+ AM departures because we were at the front of a big line to get boarding passes to get into the terminal.

It's a shame you're with AirBnB because it's not like a hotel where you could just cancel the last night and move to a hotel around the airport.
I've long since learned that those very early a.m. flights in Europe are going to take you to another larger gateway airport where you'll sit until mid day. When I'm making flight decisions, I say no to those flights. Flying home is difficult enough without starting the journey on 2-3 hours' sleep.

That's why we spent the last night at an airport-area hotel ... And arranged this year's trip into Venice and out of Rome with a mid-morning flight.

Ask your airline about their time recommendations --if you're flying to make a connection in another Schengen country, you don't need to be there before the ticket desks open. (Been there, done that.)

For our flight to CDG, we arrived 3 hours and had too much time. Two hours would give you plenty of time. check the departure times for the bus from Piazzale Roma. I think it was hourly that early, and we just missed one. We joined a business man and took a taxi to the airport, but that was a cold December morning. It looks like you might have to arrange a water taxi. If you check with the tourist information office, I am sure they could help with that.

Does anyone know how long it takes the ATVO from Piazzale Roma at 4:20am to get to VCE?

For such an early flight you can save money and add stress by figuring out public transit or sleep in a little more and have a great goodbye to Venice by reserving a private water taxi ride to the airport
(It is a decent walk from the taxi dock/dropoff to the terminal but is a flat paved walkway)

Artiving 2 hours before would be plenty of time

The ATVO bus only takes 15 minutes or thereabouts, if I recall correctly.