Sorry all, this is a long one, if only just due to the sheer number of things that went wrong.

Context:

Canadians living in Switzerland, with a child turning 2 on Dec. 20. Visiting family in YYC and YYZ for the holidays. When trying to book online, I discovered AC’s online system can’t handle a child turning two during the trip (infant vs. child), necessitating a phone booking.

Called to book in early October (1.5 hrs on hold before answer):
AC881 Dec 16 2022 ZRH-YYZ 12:45 - 15:40
AC157 Dec 16 2022 YYZ-YYC 19:30 - 21:39
AC136 Dec 26 2022 YYC-YYZ 10:00 - 15:54
AC880 Jan 1 2023 YYZ-ZRH 21:25 - 11:00

Despite strongly emphasizing that I want the seat for the child on both the outbound and return (despite the child under 2 being eligible for the lap ticket), the agent makes a mistake and books the outbound as child in lap. I noticed this same day, and called to fix it (another 1.5 hrs on hold). This is fixed, but crucially (and not obviously at this point), the agent failed to remove the lap booking, thus the reservation now contains child in lap AND child in seat. This was not known to me at the time.

I also spent quite a bit of money (~980 CAD) to get preferred seats for all 4 flights. Time passes, some operational changes happen (not AC’s fault), and the final state of booking ends up being:

AC881 Dec 16 2022 ZRH-YYZ 12:45 - 15:40 18HJK (789)
AC157 Dec 16 2022 YYZ-YYC 19:30 - 21:39 12ABC (788)
AC138 Dec 26 2022 YYC-YYZ 11:30 - 17:24 30FDE (changed on my request, no seat refund)
AC880 Jan 1 2023 YYZ-ZRH 21:25 - 11:00 18ACD (333)

Now for the actual travel experience, also consider this is all happening with a (nearly) 2 year old in tow. Actual series of events:

Dec 15 13:00
Received email reminder to check in, unable to check in the child as “passengers must be 2 or older to check in”

Dec 15 19:00 - Dec 16 05:00
Multiple notifications of AC881 delayed:
13:30 -> 14:30 -> 15:40 -> 16:55

Dec 16 11:00
Checked in the adults on the reservation to make sure to not lose the seats, noticed that one of the adults has a child in lap, checked in the lap child just in case, child in seat remains not checked in.

Called customer service (1.5 hrs hold time):

• Concerned that we will lose seats due to not being able to check in
• To rebook YYZ-YYC as it’s clear we won’t make the connection

Agent notices the mistake with the child being both on lap and in the seat, says will fix. Agent states that it’s necessary to check us out of the flight to fix the reservation, and to check in at the airport. I made it VERY clear to the agent that the booked seats are very important, and got reassurances that this will not affect the seat booking.

An overnight in YYZ is necessary at this point, booked on: AC145 Dec 17 2022 YYZ-YYC 14:15 - 16:32, 36HJK seats.

Final booking state, confirmed by documents at 11:20 Dec 16 except seats on AC145.
AC881 Dec 16 2022 ZRH-YYZ 12:45 - 15:40 18HJK
AC145 Dec 17 2022 YYZ-YYC 14:15 - 16.32 36HJK (no refund, unclear if there should be)
AC138 Dec 26 2022 YYC-YYZ 11:30 - 17:24 30FDE
AC880 Jan 1 2023 YYZ-ZRH 21:25 - 11:00 18ACD

Dec 16 14:00
Arrive in ZRH, check in, instead of 18HJK get boarding passes for 42DEG
Point this out immediately, check-in staff unsure what happened, and says 42DEG is crew rest seats anyways, but unable to give us anything except 3 seats all separate (not tenable with a 2 year old). Got “temporary” boarding passes for 3 seats apart, advised to discuss with duty gate manager Mr. Rolf at the gate. Bag checked through to YYC, stroller gate checked to YYZ.

Meal vouchers for delay provided, but told to seek overnight compensation at YYZ.

Get to the gate as quickly as possible, talk to Mr Rolf. He is unhelpful and dismissive, stating that I checked us out online, thus the preferred seats have been released because “you checked yourselves out of the flight online”. When told that the phone agent has done the checkout, Mr Rolf insisted that the computer states I have done that, and “the computer doesn’t lie” (exact words). After expressing extreme unhappiness at the events, get pointed to another line to wait.

Agent in that line eventually moves us to 33HJ + 18K (2 together, one apart), stating they will try to improve this further before boarding. This doesn’t happen, and we’re forced to sit apart. (we requested a fellow passenger to swap 33K for 18K, but they declined). No refund for 18HJ received. Talked to passengers in 18HJ, they snagged the seats around 2pm (so shortly after my morning phone call with the agent who insisted that the changes won't affect the booked seats), and paid for them, despite me already paying for them weeks earlier and not being refunded.

Dec 16 21:00
Arrived YYZ 21:16 (5h36min late), took a rental car to my family member’s house for the overnight stay. Observed that AC157 was canceled, so even an on–time arrival of AC881 wouldn’t have made a difference.

Dec 17 12:00
Back in YYZ. AC145 has a series of mechanical delays, no compensation offered. Eventually leaving 20:17 (14:15 scheduled) and arriving YYC 22:20 (16:32 scheduled, 6h12min late). The bag checked through to YYC from ZRH does not arrive, per baggage services last bag scan was in YYZ. Claim filed.

So here we are. This is by far the worst flight experience I have ever had, and I have flown a fair bit. It's now close to a day later, and no updates on the missing bag.