The Airports layer data is merged from the following Federal Aviation Administration (FAA) landing facilities databases:
- National Flight Data Center (NFDC) database for February 1994
- National Plan of Integrated Airport Systems (NPIAS) database, current as of May 1994
- Air Carrier Activity Information System (ACAIS) database for calendar year 1992
- Terminal Area Forecast (TAF) for FY91.
An Airport Code is a location identifier assigned to an airport by one of the following organizations:
- International Air Transport Association (IATA)
- International Civil Aviation Organization (ICAO)
- Federal Aviation Administration (FAA)
These codes are composed either of uppercase letters or a combination of uppercase letters and numbers ("combination codes" are only assigned to the smallest airports). For example; CYYZ is the ICAO code assigned to Toronto Lester B. Pearson International Airport near Toronto, Canada. BWI is the FAA code assigned to Baltimore/Washington International Thurgood Marshal Airport near Washington, D.C. United States.