ICAO code explained

ICAO code may refer to:

• ICAO airport code, a four-letter code designating each airport
• ICAO airline designator, a three-letter code designating each airline
• ICAO aircraft type designator, a three- or four-character alphanumeric code designating every aircraft type (and some sub-types) that may appear in flight planning
• ICAO aircraft marshalling signals, visual signalling between ground personnel and pilots on an airport, aircraft carrier or helipad
• ICAO 24-bit address, allocation of 24 bit addresses to states to uniquely identify aircraft worldwide
• ICAO altitude code aka Gillham code, an encoding used in older aircraft to report altitudes