Here’s What Those Confusing Flight Numbers Really Mean

You’ve probably noticed the seemingly random numbers and letters on your plane boarding pass before, but have you ever wondered what they mean?

Flight numbers are actually a sophisticated code meant to identify individual planes and journeys. While it’s not crucial for the average passenger to be able to understand them, it does make for a cool way to be a bit more knowledgeable about your flight.

The letter portion of the flight number indicates the airline. Delta uses DL, United Airlines uses UA, American Airlines is AA, etc.

Things get a bit more tricky from there because each airline uses a slightly different system. However, no airline can use more than five digits.

Generally, even flight numbers mean that a plane is flying north or east, while odd flight numbers indicate that the flight will be southbound or westbound.

Additionally, return flight numbers are usually one digit higher than the outbound flight. For example, an American Airlines flight from Boston to L.A. might be assigned a number like AA401, while the return flight might be AA402.

A good rule of thumb is that the lower the fight number, the more important the route is to the airline. If the flight number ends in a single digit, it was likely one of the earliest routes the airline offered.

And of course, you’re very unlikely to see a flight number that ends in an “unlucky” number like 13 or 666. People are actually less likely to want to board a plane with such an inauspicious label.