Wind and visibility information has always played a role in determining an airport's runway configuration. For a variety of reasons (including airspace constraints), considerably more attention was given to meteorological aspects for the Chicago Third Airport than is typical.
Plans for the Chicago Third Airport took into consideration many aviation related technological advancements. The runway configuration was designed to accommodate quadruple simultaneous operations. The Federal Aviation Administration requires that 95 percent of all frequent operations be accommodated by an airport's runway system. While wind and visibility statistics clearly demonstrate an all parallel runway system can accommodate more than 95 percent of all operations, there has been great debate about the ability of the runway system to actually accommodate that level of activity. Afterall, Chicago's climate is perceived to be very harsh, particularly in the winter.
To demonstrate that an all parallel runway system in the Chicago area, with it's particular climate conditions, is adequate for a planned major hub facility, significant use was made of climatological data relative to aircraft type. An analysis of the wind conditions (speed and direction) was undertaken for both a primary and a crosswind orientation. The analysis also accommodated various aircraft characteristics (aircraft gross weight, wing span and performance characteristics) during various weather conditions. VFR and IFR conditions (including numerous ceiling and visibility categories) were considered as well as crosswind conditions, wet pavement (precipitation episodes), freezing and frozen precipitation, etc