I will be visiting Paris for the first time in October 2018. I will be staying at Mercure Notre Dame St Germaine. I plan to book my flight from Paris back to the U.S.soon. My top choices are these Saturday flights: a 10:20 am Aer Lingus flight and a 2:10 pm Iceland Air flight. How early will I need to leave the hotel for the airport? (I plan to take public transportation, not a taxi.) I've read that you should arrive at the airport 3 hours before your flight so if I take the earlier flight do I need to leave the hotel by 6 am, or even earlier?
show up at the airport 3 hours before the flight; leave your hotel in Paris on public transportation 4 hours before the flight.
Use this site to research the metro schedule from your hotel to the airport
You will be close to the RER-B train line. We used this train to get to the airport recently.
If that Iceland air flight is out of Orly, public transportation to there is a little more complicated than CDG, so that's worth checking out. The taxi ride is also I think only €30 from the Left Bank. It’s about a half hour taxi ride too. In April, we left our rue de Seine apartment at 10:30 for that same flight and were at Orly in plenty of time to check in, walk to the othe side of the terminal for our gate, and have a relaxing lunch.
Two hours before should be more than enough time for either of these two flights so leave 45 minutes before that for Orly and 60 for CDG if taking mass transit. The initial flight will be considered a “domestic” flight. Personally, I’d take the Aer Lingus flight only because you can pre-clear US customs in Dublin — as far as I know, Dublin’s airport is the only European airport with that available.
Shannon has pre-clearance also.