In June 1997, O’Hare International and Midway airports agreed to use designated noise abatement flight procedures to further reduce the impact of aircraft noise at night.
The voluntary Fly Quiet Program at O’Hare International Airport encourages pilots to use designated nighttime preferential runways and flight tracks developed by the Chicago Department of Aviation in cooperation with ONCC, the airlines, and air traffic controllers.
The CDA distributes a Fly Quiet Manual to pilots and air traffic controllers that identifies preferred runways and flight tracks to route aircraft over least populated areas during the hours of 10 pm to 7 a.m. The manual is continually updated to reflect O'Hare's current runway configuration.
Adherence to the nighttime departure preferential flight tracks is recorded by the Airport Noise Management System (ANMS).