A flight number is a unique identifier assigned to a specific flight operated by an airline. It usually consists of a combination of letters and numbers, where the letters represent the airline's code, and the numbers indicate the specific route or service. For example, a flight number like AA123 refers to a flight operated by American Airlines. Passengers use flight numbers to check schedules, track flights, and find gate information at airports. When booking tickets or checking in, travelers will often need to provide the flight number to ensure they are on the correct aircraft and heading to their intended destination.