Context: I have an Aeroplan ticket YYZ-GRU at the end of December, then a domestic flight inside Brazil on another airline (on a separate ticket).

Questions:
+ Is it possible to thru-check my bags from Toronto if I have two separate tickets?
+ Are there airlines in Brazil I should favour over others to make this easier? I haven't bought my domestic Brazil ticket yet, so there's still some flexibility.
+ If I end up on separate tickets with no interlining, does anyone with experience at GRU have a sense of how much time I should leave myself for a safe connection? (collect bags, immigration, check-in again, security, etc.)

Thank you!

1. Yes - see #2
2. Interline partners are here: https://www.aircanada.com/ca/en/aco/...-partners.html
3. Sorry - can't help here.

Note that interline of baggage does not necessarily mean that AC will be able to issue you a Boarding Pass for your connecting flight. You'll need to know what facilities are airside for your respective airline for check in/issuance of BP.

I suggest sticking with the Star Alliance, if possible, which should (in theory) make interlining easier. That means using Avianca Brazil for your domestic flight. You can walk between Terminal 3 (AC) and Terminal 2 (most domestic flights, except for Azul and Passaredo). You will have to collect your luggage after clearing immigration, go landside, and drop it off again. Several airlines, including Avianca, have landside transfer desks in Terminal 3 for you to drop off luggage and get boarding passes. Turn left as you exit customs and enter the main greeting area. The desks are at the far end of the terminal, right by the entrance to the overhead walkway to Terminal 2.

It took me less than an hour to get from my international arrival gate in Terminal 3 to my domestic departure gate in Terminal 2 a couple of months ago. The line-up at immigration was short, and I did not have any checked luggage. On separate tickets, you obviously want to allow a lot more time. I wouldn't be comfortable with less than 3 hours.

Answer 1 is NO. As stated in the other response, when continuing on with a domestic flight, you must pick up your bags and clear customs. If you have a connecting flight on the same ticket, you can check your bag right after leaving the Terminal 3 secure area. If not, you will need to walk to terminal 2 (up one floor and then a 5-10 minute walk) or take the bus to archaic terminal 1 if your domestic flight is with Azul.

If it is not on the same ticket, always leave at least 2.5 - 3 hours to get your connecting flight.

Answer 1 is: YMMV, actually.

Although under no obligation to do so with separate tickets, the AC agent can add Star Alliance partner O6 Avianca Brasil on the bag tags manually which would speed up the connection process after clearing customs. If connection is with LATAM, Gol or Azul then a whole new check-in process would be needed to Terminal 2 or Terminal 1 as other FTers mentioned above.

While I don't love O6, especially if your flight is assigned one of the older aircraft plus no Star Gold lounge access for domestic flights, the checked-thru priority-tagged bags help a bit.

Thanks everyone! Very helpful advice, as usual.