To pay for a window seat on a plane, one can typically do so during the booking process. One can pay while purchasing the ticket online, over the phone, or in person at the airport. Many airlines also allow flyers to select or change their seat assignments online or through their mobile app.

To guarantee a window seat, the most reliable method is to select your seat at the time of booking through the airline's website or app. Most major carriers provide a digital seat map where you can click on a "window" icon (usually labeled "A" or "F" on smaller jets). Be aware that many airlines now charge a "seat selection fee" for these preferred spots, especially in the "Basic Economy" fare class. If you chose a fare that doesn't allow advance selection, your next best chance is to check in online exactly 24 hours before departure, which is when the remaining seat inventory is often released for free. If you are a frequent flyer with elite status, you can often reserve these seats for free at any time. If all else fails, you can ask a gate agent politely before boarding if any window seats have opened up due to cancellations, though this is a gamble on busy flights.