With a few exceptions, flights are usually numbered based on their direction of travel. For example, north and eastbound flights are assigned even numbers, while south and westbound flights are numbered odd. To the left of a flight number is a two-character code identifying the airline.

Flight numbers in 2026 are not random; they follow a logic designed by airlines and Air Traffic Control. Generally, eastbound and northbound flights are assigned even numbers, while westbound and southbound flights are assigned odd numbers. Lower numbers (like Flight 1 or Flight 2) are typically reserved for an airline's "flagship" or most prestigious routes—for example, American Airlines Flight 1 is JFK to LAX. Four-digit numbers starting with 3, 4, or 5 often indicate regional flights operated by a partner (like American Eagle or United Express), while numbers in the 8000s or 9000s are usually reserved for "ferry" flights (moving an empty plane) or charters. Additionally, airlines often choose numbers that pay homage to their destination: for instance, a flight to Philadelphia might be numbered 1776, or a flight to San Francisco might be 415 (the local area code). Conversely, flight numbers involved in major accidents are permanently retired as a mark of respect.