In the aviation industry, a flight number or flight designator is a code for an airline service consisting of two-character airline designator and a 1 to 4 digit number. For example, "BA 222" is a British Airways service from Nashville, Tennessee to London-Heathrow. A service is called "direct" if it is covered by a single flight number, regardless of the number of stops or equipment changes. For example, "WN 417" flies from Jacksonville to Baltimore to Oakland to Los Angeles on Southwest Airlines. A given flight segment may have multiple flight numbers on different airlines under a code-sharing agreement. Strictly speaking, the flight number is just the numerical part, but it is commonly used for the entire flight designator.

This is a list of airline codes. The table lists IATA's two-character airline designators, ICAO's three-character airline designators and the airline call signs. Historical assignments are also included.