You have the choice of choosing a preferred seat when checking in online. Usually, there is an extra charge for this. When compared to aisle seats, window seats are typically the most expensive. The cheapest or frequently free seats are in the middle.

Whether a window seat costs more depends entirely on the airline's "ancillary revenue" strategy and the type of fare you purchased. On "legacy" carriers like United, Delta, or American, a window seat in a standard economy row often doesn't cost extra if you book a "Standard Economy" fare, but if you buy a "Basic Economy" ticket, you will likely have to pay a fee (ranging from $10 to $50) to select any seat, including a window. On "low-cost" carriers like Spirit, Frontier, or Ryanair, almost every seat selection carries a fee, and window seats are typically priced higher than middle seats but lower than "extra legroom" or "front of cabin" seats. Some airlines have also introduced "Preferred Seating," where window seats in the front half of the plane cost more simply because they allow you to deplane faster. However, there is one major exception: the "exit row" window seat. These almost always carry a premium price because they offer significantly more legroom. If you want a window seat for free, your best bet is to check in exactly 24 hours before departure, as some airlines release unassigned seats at that time, though the most desirable window spots are usually snapped up by those who paid in advance or hold frequent flyer status.