Yes, you can almost always buy additional baggage after you have completed online check-in in 2026. Most airlines—including major carriers like Air Canada, Delta, and Air India—allow you to add checked bags via their mobile app or website right up until you arrive at the airport. In fact, it is financially beneficial to do so online; "at-the-counter" or "at-the-gate" baggage fees are typically 25% to 50% higher than the pre-paid online rates. Once you've paid for the extra bag in the app, you simply go to a self-service kiosk at the airport to print your bag tags and then drop the luggage at the dedicated "Bag Drop" counter. It is important to note that once you are at the boarding gate, your options are limited and much more expensive; some "Basic Economy" tickets in 2026 even prohibit bringing a full-sized carry-on entirely, so if you are caught with one at the gate, you will be forced to pay a "gate-check" fee that can exceed $100.