Rome 8 am flight

For an 8 a.m. flight out of Rome I would arrive three hours prior and stay at the airport. I flew into Rome and out of Florence on my recent trip, it turned out that three hours prior was more than I needed flying out of Florence but it did allow me to arrive before the lines to check in were long. Rome is a different level of busy than Florence, definitely err on the safe side.

If you are only going to Heathrow, I think three hours is excessive as an arrival interval. See what your airline recommends. I would stay in Central Rome, have a nice evening prior, and have a car service pick me up at 5:00AM. A car service, pre-arranged, should cost about 55.00 Euros.

Thank you all very much!

Very glad that in March we are only flying into Fiumicino and not out.

First trip to Italy 7 years ago, we didn't know any better so we connected to Catania, and also connected to Florence out of there on a different leg of the trip. Granted, at that time I knew only a little Italian but the lines and the arrival/departure boards were so confusing that we very nearly missed both flights. And not that I'm generalizing (Roberto!)--because I am Italian myself--but the workers seemed much more concerned with how they're dressed and socializing with each other than with helping travelers who might be standing in the wrong line for a half-hour. Yes, that would be moi.

However, I did have the best airport meal of my life at Fiumicino, an incredible antipasto plate at Cafe dei Frescobaldi, which looks to be a chain of sorts. So there's that!

The airline requires that you have checked in your baggage and have the boarding pass in your hands at least 45 minutes prior to departure. That would be the minimum.
Be in line at the check-in counter 90 minutes prior to departure and you will be at the gate with plenty of time to spare. You are on a European flight and 3 hours would be excessive even for a transatlantic flight.