IATA Airport Designator Information
IATA Three letter Airport location Code
Please note that IATA three letter location codes are not just used to identify airport locations.
They are also used to identify locations for Cities, Bus/Train stations and Harbours/Ports. City codes are listed as Metropolitan Areas.
Examples
LON = London / Metropolitan Area - Is a City Code
LHR = London - Heathrow Airport - Is a Airport Code
QQO = London - Paddington / Rail Station - Is a Location Code