What is the standard two-letter identifier assigned to an airline by IATA called?

The standard two-letter identifier assigned to an airline by IATA is called an IATA airline designator.

The International Air Transport Association assigns these designators to identify airlines in reservations, timetables, tickets, baggage tags, and flight numbers. The designator usually consists of two letters, although some identifiers use a letter-and-number combination or two characters from the permitted system.

For example, British Airways uses BA, Lufthansa uses LH, and Air France uses AF. These identifiers commonly appear before a flight number, such as BA flight 202 or AF flight 7. The designator is an airline identifier rather than the name of a particular airport.

The main confusion is with the ICAO airline designator. ICAO designators are generally three-letter operational identifiers used in flight plans and air traffic communications; British Airways, for example, uses BAW. A radio callsign is a related but separate operational term.