If your carry-on exceeds Air Canada's strict dimensions of 21.5 x 15.5 x 9 inches (55 x 40 x 23 cm), you will be required to check it at the gate or the check-in counter. In 2026, gate agents actively use sizers to verify bag dimensions during the boarding process. If your bag is deemed "oversized," it will be tagged and placed in the aircraft hold. Crucially, if you have already used your checked baggage allowance or if your fare type (such as Economy Basic) does not include a free bag, you will be charged the standard checked baggage fee plus a potential gate-handling surcharge. This can result in a significant unexpected expense, often exceeding $50–$100. Furthermore, if you are forced to check your bag at the gate, you must remember to remove essential items like medications, travel documents, and lithium-battery devices (laptops, power banks) before it is taken, as these are prohibited in the cargo hold.