That AF flight is an A350-900, so expect them to begin boarding about 5 - 10 minutes after you land (assuming on-time arrival in YYZ) and expect the boarding area to be a complete zoo by the time you get there. GE is of no use but Nexus, if you have that, will help. Carry-on only will also help. Regardless, it's going to be a close shave even if everything goes your way. Good luck!

Why did I think GE applied at Canada airports as well? Sounds like I should find an alternative. The YYZ-CDG leg I bought on delta.com, the DTW-YYZ will be purchased separately (also on delta.com). Thanks.

Thanks to you and Symmetre inputs on this. On the outbound, it was a breeze as US travelers weren't subject to any additional security checks. Had plenty of time to grab food in one of the many options available. On the inbound leg, most of the time taken was in clearing the security. The GlobalEntry line was a breeze. The food options near the high numbered F gates were sparse. I wasn't eligible to use the lounge, so had to make do with coffee store snacks ;)

Agree, very tight. I understand GE doesn’t impact your connection in YYZ since it’s designed for U.S. customs (I am missing something?)

AS from Sea to BA LHR via YYZ
 

One itinerary. I am flying from Sea to yyz on Alaska and from yyz to lhr on BA with terminal 3 transfer. Is there a passport or Canada immigration required and then being dumped outside sterile area to be re-screened again.
I hope us to internarional connections at terminal 3 don't require entering Canada. Yyz connections guide talks about cleaning Canada immigration in this case at terminal al 3.
any other info thanks

So far as I know you will need to clear Canada Customs upon arrival in Toronto. It's super-quick if you have Nexus (NOT Global Entry). If not, then consider downloading the advance declaration app to save a bit of time.

Once you clear customs, you'll most likely need to collect your checked baggage, then head upstairs to the departures level and re-check them (I don't know if Alaska can check bag through to final destination, you'll have to have them verify that). In either case, you will then re-enter security, and proceed to your gate. Both Alaska and BA operate from terminal 3, so at least it's not that long a walk. Unless you have a super-tight connection (>90 minutes), you should have time to spare.

YYZ T1 (Air Canada) has this but T3 does not. So you need to formally enter Canada.

thanks

SFO-YYZ-DXB with 1.5hrs tomorrow. Thoughts? SFO-YYZ was 4hrs delayed today because the incoming flight was 4hrs delayed getting out and weather is supposed to be just as bad tomorrow.