How to travel from Venice to Airport very early flight

This topic comes up often here are some replies:
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Your questions comes up somewhat frequently.

The solution I used is to transfer to a hotel near to the airport and outside the car free zone. One example is the Courtyard by Marriott Venice Airport with a shuttle to the airport. Our group overnighted at the Smart Hotel Holiday Venice, a 6 km taxi ride to VCE.

My solution for an upcoming trip is to stay in accommodations close to the Piazzale Roma, and catch a bus from there to the airport - the busses start running at 4:20 a.m.

The first ATVO bus is at 4:20, the first ACTV No 5 bus is at 4:35 M-Sa, 5:40 Su.
To get to Piazzale Roma, the "N" boat goes from San Marco-S. Zaccaria "E" dock in front of the Danieli Hotel at 3:47 and will get to Piazzale Roma at 4:20, in time for the first No 5 bus at 4:35 and getting to the airport at 5:00, plenty of time for a 7 am flight.

I would just say that arriving at the airport at 5 AM for a 7 AM departing flight would make me very nervous. We have a family member with some mobility limitations and artificial joints, which always set off the x-ray machines, so we have learned to allow extra time to get through security even on domestic flights. If you're not dealing with those kinds of issues, then 2 hours may be fine. I would just find it stressful cutting it that close.

Just put your "headline' in the search bar ( top of page) and you will find an almost endless list of discussions on the topic.

Leaving the hotel at 5AM for a 7AM flight is 99.999% certain to end badly

2 hours is not cutting it close at Venice airport. Even if coming back to North America, it will be connecting at some other European gateway, so it is bound to be a "domestic" flight. If you arrive much earlier than 5 am, there might not be anybody there to check you in.

Edit leaving your hotel at 5 am, better have a water taxi booked, and you probably will not get to the check in desk until 6 as it is a long way from the dock to the airport, even with the new moving walkway.

Another important factor is where the flight is going.

If it lands in a non-Schengen country you will have more 'departure processing' to get through, than if going to some other Schengen country.

You could take an early vaperetto down to the train station and have a taxi take you to the airport.

I'd be staying at the Courtyard by Marriott out at the airport, as it's priced cheaper than most accommodations in Venice.