Hopefully the passport is less than 10 years old, and is still valid! If you are even eligible for a British passport you can't get an ETA.
I flew to the UK 3 weeks ago and had zero issues checking in-online using a British passport. And no problems on the way back using my Canadian one. I didn't fuss about any existing profile.

You can renew British passport up to 6 months before it expires, the "balance" gets added to the expiry date on your new passport (wish Canada can do the same). My passport is indeed over 10 years old and it doesn't expire until April 2026.

I don't look anything like the picture though, I was at least 20kg lighter back then but I digress. I'm more concerned about AC's GA than the border force to be honest, they can get pretty creative when pulling new rules out of their bottom.

Thanks for the information, I will try checking in with my British Passport.

When the UK ETA system is fully implemented (it was on a transitional phase � not sure if it still is or not), you won�t be able to check in online without an ETA, UK passport, or UK e-visa. I think a check-in agent at the airport can override it if you show them a physical visa, but those are supposed to be phased out by now too. I think this is all very similar to the Canadian ETA � I wasn�t able to check in online a couple of years ago until I replaced my UK passport with my Canadian one in my PNR.

Up until this year I usually just had my Canadian passport in my PNR and just used my UK one at the LHR immigration kiosks, but have now been putting my UK passport in for the outbound trip and replacing with my Canadian one for the return.

I had my UK passport on the file. No problem for YYZ-LHR part of the itinerary. Return was CDG-YYZ I could not do online check-in because I did not have an ETA (as a Canadian citizen did not need one) so could not complete the process. Was informed that only AC staff could change the passport on the file. Irritating because I had no checked baggage and expected to go right to security.

Went to check-in at CDG. It took close to an hour for a kind and experienced agent to do whatever needed to be done to get the boarding pass. I have no idea why this was so complicated.

After this and based on advice from FTers, I keep my Canadian passport on the file and simply use the UK passport on arrival at Heathrow. No issues whatsoever. Have done this numerous times.

I have not done it since the UK implemented new entry requirements. Wondering if this strategy will still work.

You can 100% change the passport back to your Canadian passport yourself online for the return leg. There are 2 ways: first is to update the passenger information page after you click check-in on the app but before you actually start the check-in process, or, as someone else mentioned above, hit the Back button during the check-in process when it asks for the ETA details and replace the passport info with your Canadian passport. Not exactly intuitive but when once you do it it�s easy enough on later trips.

It is interesting this ETA business - between the confusion aorund Brazil and the Canada-GRU-EZE stopover, and this UK & EU business, we've just gone back to needing visas to go anywhere. With the complication this starts to add, maybe AC's website/system profiles will be expanded to add support for multiple passport (or destination-based IDs).

I imagine it will cause quite a bit of hassle if you check in without an ETA and just show them a UK passport at boarding.

What's interesting is that it's just AC's systems that don't seem to be able to support multiple passports -- Amadeus' systems can. A few months ago I flew an AC/LX connecting trip, and on the returning legs I changed the passport on my PNR back to my Canadian passport. The AC website showed just the 1 passport (the last one I put in), but LX's website (and they're also on Amadeus and shared the same PNR number) it showed BOTH passports on the booking.
You literally can't check in for a flight to a country that requires an ETA if you don't have one. UK may still be transitioning so it may still be possible right now, but once it's fully implemented online check in will be blocked unless you switch your passports over in the PNR.

Thank you for this guidance. I was definitely informed it could not be done.by an pax after booking (ie, make a change to security related info). Only AC staff could do this. However, I don’t work at the airport or the call centre. I never tried again because the work-around solved my problem.

Perhaps they made a change to the site. My experience was shortly after Canada introduced the ETA. Sounds like I should go back to doing what I used to do.

It would be very easy if one-way tx to/from Europe were priced differently (more like NA)L That's a whole other discussion.

I'm getting off topic here, but I assume that an Irish passport will also work since it doesn't require an ETA and AC will let you check in with that.

I was just looking at an upcoming booking YUL-YYZ-SCL. It says in the app "Your upgrade to Business Class is confirmed," alongside the little upgrade symbol. But I paid for J. Is this normal? When I look at my receipt or if I go to manage my booking it correctly says Business (P).

I try to book a flight and the first time I press the purchase, I got an error saying my credit card was not accepted and try again. I tried another time, same problem. I went to my laptop (I was on my ipad) and try to book, it went through.
But when I requested an upgrade, I saw that I have 3 bookings. When going into 2 of the bookings (the ones in error), I see the flight but I'm not able to manage the flight. So is this a real booking and should I be concern that they will eventually charge me 3 times?
Thanks

They should drop off in about an hour or two, in my experience.

Bookings aren't refreshing right now on the website or app. A couple of new bookings did not show up and an adjusted one is not showing as changed on neither the website or app. When I check manually, all is good. Anyone else experiencing this?

The web site has decided not to show many any options for Aeroplan bookings. I was looking at a bunch of options last night ... I had many, many search windows open ... and everything was working fine, until it wasn't. All of a sudden, I stopped getting any flight options displayed at all. I can still see flights when I search for cash fares, but when I search for the same flights using Aeroplan points, all I get is a message "There are no flights available on the date you selected, but there may be flights on other days. Modify your search for more options (generic)".

I get this message no matter what dates nor destination I'm searching for ... it's almost like the AC system thought I had searched too much last night, and started to block me. I gave up last night, but the problem persists this morning - even after logging in again, I don't get any search results for any date nor destination when I try to use Aeroplan points.

Has anyone else seen a problem like this?

Interesting Data point? Booking YUL-China Open Jaw-YUL leaving late November returning early December in PY. AC Website was $1000 less with better connections and more AC metal that GF. I don't recall seeing this much discrepancy between AC.com and GF before.