TagFour Post Plan(18)

In 1992, the Ninth Circuit Court of Appeals upheld the FAA's decision to change flight patterns for turbine-powered aircraft at Seattle-Tacoma International Airport without preparing a full Environmental Impact Statement. The FAA had issued a Finding of No Significant Impact based on a computer noise model using the 65 decibel day-night sound level as the threshold for significant noise impact, which the court found to be a reasonable approach. The Seattle Community Council Federation had challenged the decision, arguing that the FAA failed to adequately assess the noise effects on surrounding communities.

These two Port of Seattle Flight Track Sample maps compare jet aircraft arrival and departure patterns at Seattle-Tacoma International Airport (SEA) under south flow conditions, one from March 22, 1989 (pre-4 Post) and one from March 31, 1991 (4 Post). Both charts plot all jet flight tracks between approximately 4:30–24:00 and 6:00–22:00 respectively, showing how flight paths over the Seattle region shifted between the two periods. The maps are annotated to highlight southbound departures and arrivals over Seattle, serving as visual evidence for noise impact analysis related to airport runway and procedure policy changes.

On April 2, 1990, the FAA announced it would implement the 'Four-Post Plan,' a set of air traffic control procedural changes at Seattle-Tacoma International Airport designed to reduce congestion, improve efficiency, and address worsening arrival delays. The plan, developed after nearly a year of public meetings, environmental review, and computer simulation of 13 alternatives, was determined to produce no significant noise impact on surrounding communities. The FAA cited a 30,000 increase in annual landings and takeoffs since 1988 and the failure of mediation talks to produce an agreed-upon flight path solution as key reasons for moving forward with the changes.

This 1990 document outlines a comprehensive package of noise abatement actions for Seattle-Tacoma International Airport, agreed upon by a Mediation Committee on March 31, 1990. It covers measures such as nighttime flight restrictions, soundproofing programs for nearby homes and public buildings, improved flight corridors, and a new noise management monitoring system. According to the technical consultant involved, full implementation of these agreements could reduce noise levels by approximately 50% for communities surrounding the airport.

This 1980 Federal Aviation Administration order establishes noise abatement procedures for aircraft operating to and from Seattle-Tacoma International Airport and Boeing Field. It directs turbojet aircraft to fly over Puget Sound and Elliott Bay whenever possible, sets altitude and distance restrictions before aircraft can turn toward populated shoreline areas, and defines preferred takeoff and landing runways to minimize noise impact. The procedures apply to both VFR and IFR turbojet flights, with stricter nighttime rules between 2200 and 0600 local time.