At the outset, airports were generally located out in the open rural spaces...few, if any, buildings etc.
Then the airports became surrounded with houses, businesses and buildings in general. This produced the well-known city "heat island" effect and suddenly the archived temperature readings from these airports showed a definite upward trend.
This phenomenon invalidates a lot of so-called global warming via temperature records.
I grew up in a rural area. The temperture "in town" was always a couple degrees warmer than out in the country where we lived.
You can add to that the fact that weather stations were moved to big airports as modern ones were built. In the 60's Houston's reporting station moved from a couple of miles off Galveston bay to 50 miles inland at what is now George Bush International. Warmer summers, though the weather never changed.