In accordance with FAA Order 8260.54A (Paragraph 2.10), the maximum authorized glide path angle for 99 percent of aircraft that approach O'Hare is 3.1 degrees. The 3.0 degree glide path has been determined to be the optimal approach glide path angle for all aircraft, from an operational safety perspective. For O'Hare the 3 degree could only be increased to the maximum allowable 3.1 degrees in order to clear obstacles. There are no obstacles in the runway approach at O'Hare, therefore all O'Hare approaches operate with a 3.0 degree glide path angle and must operate in that manner.
According to the FAA, "the City of Chicago has stated, at ONCC Technical Committee meetings that they would be supportive of considering and analyzing modifications to their current Fly Quiet Program once the O'Hare Modernization Program (OMP) is completed. Any interim changes (before OMP completion) to the currently approved Fly Quiet Program would need to be approached through discussions between the City of Chicago and ONCC. Such discussions would require consultation with the FAA and may require some degree of environmental review.