On most narrow-body commercial aircraft (like the Boeing 737 or Airbus A320) that follow a standard 3-3 seating configuration, the "F" seat is a window seat on the right-hand side of the plane. In this layout, the seats are labeled A, B, and C on the left side, and D, E, and F on the right side. Therefore, "A" and "F" are the window seats, "B" and "E" are the middle seats, and "C" and "D" are the aisle seats. If you are flying on a larger, wide-body aircraft with a 2-4-2 or 3-4-3 layout, the "F" seat is usually an internal aisle seat or a middle seat within the center section of the plane. For example, in a 3-4-3 layout, the seats might be A-B-C (window/middle/aisle), D-E-F-G (aisle/middle/middle/aisle), and H-J-K (aisle/middle/window). Knowing that "F" is traditionally a window seat on smaller planes is a helpful rule of thumb for quick seat selection, but you should always consult the specific seat map of your aircraft during check-in to ensure you aren't ending up in the middle of a four-seat center row on a long-haul flight.