Yes, you can pay for extra baggage at the airport for international flights, but it is the most expensive way to do so. Airlines like Air India, United, and Lufthansa charge significantly higher "at-counter" rates compared to pre-purchased online rates. For international routes, fees are often calculated by the "piece concept" (paying for an entire extra suitcase) or the "weight concept" (paying per kilogram). For example, adding a bag at the airport for a transatlantic flight can cost between $200 and $250 per piece, whereas pre-paying online often saves you 20% to 50%. Additionally, if your bag is both "extra" and "overweight" (over 23kg/50lb), you will be charged dual fees, which can easily exceed $400. To avoid these astronomical costs, use the airline's mobile app to "Manage Booking" at least 24 hours before your flight. Also, be aware that some smaller regional international flights have strict weight limits due to aircraft size, and they may refuse extra bags entirely if the plane is at capacity.