July 2, 2026
How the FAA Designates US Airports: The K Prefix Explained
Every airport in the contiguous United States has an ICAO code starting with K. But the FAA also has its own identifier system. Here is how US airport codes work across multiple systems.
The United States has more airports than any other country — over 19,000 public and private airfields. These airports are identified by multiple overlapping code systems: IATA codes for commercial airports, ICAO codes for all airports, and FAA Location Identifiers for the FAA's own systems.
The ICAO K prefix
All airports in the contiguous 48 states use the ICAO prefix K. This means the ICAO code for most US airports is simply K + the airport's IATA code or FAA identifier. Seattle-Tacoma is SEA (IATA) and KSEA (ICAO). Los Angeles is LAX and KLAX. Denver is DEN and KDEN.
Alaska and Hawaii
Alaska and Hawaii use different ICAO prefixes — P for the Pacific region (which includes Hawaii) and PA/PF/etc. for Alaska specifically. Anchorage is ANC in IATA and PANC in ICAO. Honolulu is HNL and PHNL.
FAA Location Identifiers
The FAA assigns its own three or four-character identifiers to all airports under its jurisdiction, including private strips that have no IATA or ICAO codes. FAA identifiers for major airports typically match the IATA code. For small airports without IATA codes, the FAA identifier may look like 3S7 (a number followed by letters) — these never appear in IATA or ICAO systems.