The logic behind this is that the letters A and K will always be window seats. The letter K is chosen, because it's the highest that you can go in a normal airplane with 10 seats across (An A380 for instance). I is omitted because of it's resemblance to 1.

In 2026, seat K is almost always a window seat, particularly on large wide-body aircraft used for long-haul international flights. Airlines typically use a standardized lettering system where "A" is the window seat on the far left of the plane and the final letter of the row—frequently "F" on smaller planes or "K" on larger ones—is the window seat on the far right. On a typical 3-3-3 or 3-4-3 configuration found on a Boeing 777 or Airbus A380, the seats are usually labeled A-B-C (Left), D-E-F-G (Middle), and H-J-K (Right). Note that the letter "I" is skipped to avoid confusion with the number "1." This makes "A" and "K" the most "coveted" spots for travelers who want to see the view or have a wall to lean their head against while sleeping. However, always check the specific seat map for your flight, as some budget airlines or smaller regional jets with 2-2 seating may end their rows at "D" or "F," making those the window seats instead.