Trends in IFR conditions at major airports in the United States

Weather continues to be a major factor in costly commercial aviation delays. This raises the question of whether or not there exist trends in inclement weather conditions over time. Restricted visibility and low cloud ceilings will cause air traffic controllers to issue instrument approaches, as opposed to relying on visual separation of aircraft as they arrive. These approaches, performed under Instrument Flight Rules (IFR), require greater separation between aircraft, which reduces the arrival capacity of the nation’s busiest airports by a considerable amount, potentially leading to delays. Since these conditions are closely tied to moisture profiles in the atmosphere, it stands to reason that their prevalence may be changing with the climate.

A multi-decade analysis of surface conditions and cloud ceilings is performed, utilizing archived surface observations from the 30 busiest airports in the United States. Trends are calculated for the frequency of IFR conditions from 1973 to 2017, the relative contribution of low-visibility and low-ceiling conditions, and the associated surface conditions that give rise to such an environment. Significant changes are found at most of these airports, suggesting a considerable impact on commercial aviation operations across the United States.