I'll be flying YYZ-GRU-SDU on Air Canada and Azul. I'm wondering if anyone knows how it works with the baggage at GRU. I assume I have to get the baggage for customs, but am I allowed to re-check it right away, or do I have to go through check-in with AZU at terminal 1?

I used to travel multiple times a year to GRU connecting to Azul. Unless something has changed since last year (unlikely) you would go through immigration & customs, then collect your bags from the belt, and drop it off at the bag drop past the baggage claim exit.

Then you exit the terminal and catch the T1 bus (green). Pretty easy.

Wonderful. That's what I expected but I wanted to confirm. Thanks a lot.

As described above is the base plan however more than once have I exited customs only to find the line to re-check be a hundred+ people deep and moving very slow. I’ve waited an hour in that line so now if I see it super long I head straight to whatever terminal I’m going to and re-check in from the normal line. There is no guarantee that line will be shorter but i haven’t been burned by it yet.

Why do you need to re-check in? As long as you drop your luggage, go to the terminal, pass security, check the gate and wait for the flight.

Cheers!

It is not that simple. When you "drop" the checked luggage, you interact with an agent, and they want to see your identification and boarding pass to confirm everything. Plus, the agent will provide their version of a boarding pass for the domestic flight which is likely different from what you originally received. Additionally, depending on the originating carrier, you might not receive a boarding pass for the Brazilian domestic flight, just a piece of paper to indicate you have a flight. Also, in this case, the Azul app recently is horrendous. If you enter the Azul confirmation code you originating carrier provides, Azul generates a new confirmation code (if it actually works). You may or may not be able to use this new code to actually see a boarding pass for Azul in their app.

I am sorry you have to go through this. I have been to Brazil quite a few times over the last 10+ years and only experienced this one time when the agent was not at the carousel to transfer the bags. Have you tried using the ATMs and entering your information to get the boarding pass? Usually, there's an agent there helping people. Good luck on your next flight, and keep us posted.