온라인이든 직접공항에서 내든 상관없네요.
그리고 fee도 약간 더 낮은것 같구요
맨 아래 링크 확인해 보시길

How to Pay Baggage Fees
You can pay any applicable baggage fees when you check in for your flight:
online,
on your mobile device,
at the airport using one of our self-service check-in kiosks
at an Air Canada check-in counter
Note: For transactions conducted outside Canada, baggage fees will be charged in the local currency of the country in which the transaction occurs.
Baggage fees are not refundable if your bags are delayed.

1st bag
$26.25 CAD/USD
(per direction, including taxes)
Flex and Latitude fares - 1st bag free

2nd bag
$36.75 CAD/USD
(per direction, including taxes)
Latitude fare - 2nd bag free

Each additional bag:
$105.00 CAD/USD
(per direction, including taxes)

No overweight or oversize charges apply when the additional bag fee is paid.

https://www.aircanada.com/ca/en/aco/home/plan/baggage/checked.html

저희는 공항에서 현금으로 지불했어요~