· Flight numbers along a specific route can remain unchanged for years barring any sort of incident. Before September 11th, American’s daily from Boston to Los Angeles had been flight AA11 for decades.
· Traditionally, flights going eastbound or north are assigned even numbers and those going west or south get odd numbers. But, it isn't uncommon to see exceptions to this rule due to differences in airline policies.
· The lower the number, the more “prestigious” the flight route is for that particular airline. And by prestigious, we mean in terms of popularity and profitability. One or two-digit numbers are typically assigned to popular long-haul routes. United Flight 44 from Newark to London, for example. Another great example: American Airlines 1, between New York and Los Angeles.
· Flight numbers comprised of four-digit sequences starting with 3 or higher are an indication of a code-share flight. Think “express” routes where you are flown between destinations “on behalf” of an airline.
· Return flights between destinations are often assigned a number that is one higher or lower than the outbound flight. So, if you were flying roundtrip from Philadelphia to St. Maarten, U.S. Air flight 1209 would take you down to the Caribbean (southbound) and flight 1208 would bring you back to the States (northbound).
Remember, perfection has never been the airline industry’s cup of tea, so understand that there are exceptions. We find it pretty interesting though, and as it turns out, comparing the flight numbers on the monitor to the routes they fly is actually not a bad way to pass the time during a delay.