Air Canada to Europe...clear customs?

Anita, I've changed planes in Montreal on a flight to Paris, but didn't have to "clear Customs" (perhaps because my flight originated in Canada). As your flight originates in the U.S., the procedure may be different? I don't know the answer for sure, but hopefully one of the others may have more information. Happy travels!

I changed planes in Toronto for a trip from Chicago to Dusseldorf in 2010. I see that I have a "Canada Customs" stamp in my passport, so I guess I did. Wasn't much more than "How long will you be in Canada?" A: "Long enough to get on the Lufthansa Dusseldorf flight." Returning, we cleared US customs in Toronto as the Air Canada flight deplanes at the domestic terminal in Chicago.

Pearson International currently posts this information on its site about connecting to the United States through Terminals 1 and 3: "If your baggage is tagged to your connecting flight, proceed to the US Customs connection baggage claim belt in the corresponding terminal to retrieve your baggage by following either the A or F connections signs. Flights departing from gates A are located in Terminal 3. Flights departing from gates F are located in Terminal 1. Once you have your baggage proceed through US Customs & Border and Protection for processing, followed by security screening. "If your baggage is not tagged to your final destination, follow the Baggage Claim signs to retrieve your baggage, and then proceed to your departing airline's check in area. "For further information please refer to one of the various Connections Centres and flight information screens throughout the terminal." There is no mention of going through Canadian entry procedures. The link is http://www.torontopearson.com/Connecting.aspx#
A project to streamline this process through the use of scanning equipment so that luggage does not have to be retrieved is planned for several Canadian airports. I don't know what stage it has reached.

I flew Air Canada a couple of times to/from France, and indeed we cleared U.S. customs in Canada , but it was on the return trip. I.e. flew from Paris CDG to Montreal, cleared U.S. immigration in Montreal (??!!) and then flew on to Washington National. I loved it, as it meant I was footloose and fancy free upon my arrival in DC; all the formalities had been taken care of in Canada. I have no idea how they set this up or why the Canadians agreed to it, but I found it terrifically convenient!

Anita: Some countries have "transit" passengers, where you are allowed to change planes without formally "entering" the country. For instance, when I flew from San Francisco to Bangkok through Taipei, I never "entered" Taiwan, but just went from the first plane to a transit lounge to the second plane, with no immigration or customs formalities in Taiwan. But the US does not have this. If you are flying from London to Mexico City via New York, you have to go through customs and immigration in New York. Even though you would just be "in" the US for a few hours, you would have to get all the necessary paperwork as though you had a longer visit (ESTA, visas, etc). Apparently, Canada also has no "transit" passengers, with some very limited exceptions. Leaving Canada and going to the US, you go through US immigration and customs on departure rather than on arrival. In other words, coming from Geneva to Montreal, you will "enter" Canada and "leave" Canada, then "enter" the US - all in Montreal Airport. Your arrival in the US is then like a domestic arrival. The Montreal Airport website isn't as detailed as some others, but here's their page on connections:
https://www.admtl.com/Passengers/Formalities/ConnectingFlight.aspx

Harold is ABSOLUTELY CORRECT.

From the airport web page U.S.-International If your flight originated in the United States and you need to take a connecting flight to an international destination, there are two possibilities: If your airline offers the option of automatically transferring your luggage, you must go to the special international connections customs counter.
If your airline does not offer the option of automatically transferring your luggage, you must pick it up yourself from the carrousel, then follow the normal procedures for international arrivals, then for international departures. In other words, if you are on the same airline, or perhaps partner airlines and your bag is checked through to your final destination, you do not have to pick up your bags - they will be automatically transferred to your flight to Geneva. You will have to clear Canadian customs, but there is a dedicated faster track for this as you are continuing on to another country. In Toronto you don't need to reclear security if you go through the dedicated international transfer connections customs counter and I believe this is true in Montreal also - you stay "airside" so you don't reclear security - but you do need to go through customs.

One more post on this for Anita - the special customs line for passengers in transit is typically far less busy than any other customs line and may even be in a different location. Your airline should have booked a sufficient transfer time to include the customs clearance. If your entire flight is on Air Canada, you should be fine. If you booked separate tickets or tickets on different airlines you will definitely need more time because you will have to clear regular Canadian Customs, pick up your bag, re-check them on your second flight and clear security again. I hope you have a ticket from LA to Geneva which happens to have a stopover in Montreal. Then it will be easy.

I don't see why I'm absolutely incorrect (and in bold, oh my!). I went through Canadian customs, and then through U.S. immigration, all in Montreal on my way back from France to the United States. And this, more than once. People citing the websites of the airports clearly back up what I've said. Sheesh!