Get to the airport two hours early?

One and a half hours is not enough time between a long-distance train arrival and a transatlantic flight. The problem for me isn't so much time spent passing through the airport as the risk of delays to the train. I would always travel to Paris the previous day and spend the night.

For CDG? No way, 1.5 hours is way too close. Any train delay and you miss your flight. Normal CDG chaos and you miss your flight. Does the train arrive near your terminal, or is a terminal change required? When does your plane board? More like 1 hour after you arrive, right? The flight boards before departure, and if you're not there...

Yes, it's possible to do it in 1.5 but not all the time - there is a real risk of missing the flight. I leave 3 hours for CDG, which is often recommended for intl. 2 would probably be fine

Maybe there's a shuttle or car service from your small town that leaves earlier than the train?

http://www.cntraveler.com/stories/2014-07-11/ombudsman-the-tao-of-airport-arrival

If it is actually flying back to Montreal or Toronto, it is at Terminal 2 where the train station is. If it is a code share on United to San Francisco, Washington, or Chicago, United goes from Terminal 1. That would be impossible. Check Air Canada's check in requirements. United pulls the check-in desk agents 1 hour before the flight to go and work the gate.

3 hours is the recommended time for international flights to the US. Remember all the security theatre you will have to endure and the queues that will build.

CDG in particular is difficult and huge.

As Clint Eastwood once famously said - Are You Feeling Lucky?

The big question I would be asking is - if you miss that flight can you financially afford a new ticket at full price on the next flight, do you have anything pressing to do when you get home if you are delayed (like going to work), and how do you deal with stress? Or maybe, you are on a fully flexible full priced ticket and it doesn't matter.

Dunno.

I know which I would do.

Yes, it would be easier to just catch a train in the morning .... almost as easy as catching a train the night before. Get yourselves to Paris the night before, take a room at the Ibis hotel right at CDG, and save yourselves a lot if stress. By the way, where did you get the idea that 2 hours is enough time for an international flight? Especially at CDG 3 hours is the norm, carry on luggage notwithstanding.

Get to Paris the night before, get to CDG three hours before your flight, have breakfast at the caviar bar.

Just to repeat what others have said, you need to allow at least 3 hours at CDG.

For CDG, it's easiest to arrive in Paris early and stay at one of the hotels at the airport. On a recent trip, we had an 8:30AM flight on a Sunday. We left the hotel and entered the main terminal at 6:30AM. From this point, it took us about 45 - 50 minutes to get through customs, security, and walk all the way to our gate. And this was with no gate changes, and without hitting any snags along the way. Had there been a security line of any length, it would have been much longer.

I never mind sitting at the gate for a while. I would always err on the side of caution, especially on a transatlantic flight.

And I do agree with what others are saying about allowing 3 hours at CDG. Had our flight been later in the day or on a particular bad day of week, we would have been there earlier.

3 hours is 3 hours for a reason.
Your flight will start boarding an hour before departure.
I've stood in line at CDG to check in for an hour. This was on AA, with about 3 flights leaving close together, so another airline could be different.
Even with carry-on only, you still need to get through security.

The first train gets you to the TGV station at the airport 1 hour and 15 minutes before the flight? And then you have to get to whichever terminal your flight departs from?

Allow me to add to the chorus of voices suggesting that this is not a good idea.

If you do decide to stay at a CDG-area hotel the night before, be sure to ask if there is air conditioning in the room, if that is important to you, especially in August.

Air France last week suggested arriving at CDG 3 hours before scheduled departure time, and that's what we did.
You probably want to think carefully about this. It's high stakes. If you miss your flight, the airline will consider it your fault, and that could get expensive and inconvenient for you.
Don't end your trip with a hassle, when you don't have to.

My first experience at CDG 15 years ago was so chaotic I was gunshy and made sure to get there way, way early this time. Especially since my wife had to process some VAT refund paperwork.

The front of the airport (the airline desks) went very smoothly, the tunnels went well, and then wham - major backup at the actual security area. That's when I started to get nervous, even though we were flying in business and had "VIP" checkin cards. It's just a matter of too many people trying to do the same thing all at once in a small space.

At least one of the guards had a sense of humor. He pulled me out of line and told me to raise my leg. Then he told me to raise the other. When I did, he said no, both at once. I said if I could do that I would be in Cirque du Soleil and we all laughed. Luckily.

Also note if you have airline or hotel miles, there's a Hilton at CDG that is absolutely right next to the shuttle station.

1) There is no guarantee that you will be able to do online check-in the night before the flight for any number of reasons (getting flagged for a random secondary screening is not uncommon and will generate a requirement that you check in at the airport) So you need to plan with the idea you might have to check in at the airport.

2) The hard deadline for AC international check-ins is 60 minutes. So you're doing a lot of gambling that not only will your train be on time but also you can exit the train, get to the AC check in desk or kiosk and then there won't be enough of a line there that you can get boarding passes in hand before the clock turn over to 59 minutes, at which time the airline can declare you to be a no-show.

3) As others have said, it's an irrational risk to take.

Air Canada takes a hard line to the check in deadlines even with carry on only. I used to travel for work mostly using Air Canada. We were warned and some colleagues had very close calls.

You should consider how far you are travelling, the likelihood of train delays, the consequences of missing the hard check in. Then, as the saying goes, govern yourself accordingly.

I've heard the Ibis at CDG is reasonable.

Thanks for all of your advice. We discovered that we can get an earlier train into the Monparnasse train station, then take the bus or RER to the airport and get there three hours early on the day of our departure.
Happy travels, everyone.