Flight number

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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.^[1] For example, QF9 is a Qantas Airways service from Perth, Australia 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, QF1 flies from Sydney to Singapore to London on Qantas Airways. 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.

The flight designator of the operating carrier of a commercial flight is used as a call sign.^[2] This is distinct from the aircraft's registration number, which identifies a specific airplane.