What airport is PHX?

Why the code is PHX

PH for Phoenix, plus the filler X.

The airport authority or a contemporaneous record states this directly.

The airport

IATA code

PHX

ICAO code

KPHX

Airport

Phoenix Sky Harbor International Airport

City

Phoenix, United States

Code origin

Documented

Sky Harbor is unusual among big US airports in sitting four miles from downtown, inside the city rather than out on cheap land. Summer heat is an operational constraint rather than a comfort one: thinner hot air reduces lift, and in June 2017 a run of 48 °C days grounded regional jets whose manuals simply did not have a chart for that temperature.

The other code, KPHX

Every airport has two codes. The three-letter IATA code, PHX, is the one on your boarding pass and your luggage tag, and it is assigned for commercial use. The four-letter ICAO code, KPHX, is the one pilots and controllers use, and it is assigned geographically: the first letter or two identify the region, so every airport in the same part of the world shares a prefix. That is why KPHX looks nothing like PHX.