In August 1987 the National Parks Overflight Act (NPOA) mandated that the FAA and National Parks Service (NPS) work together to achieve “substantial restoration of natural quiet” in the Grand Canyon National Park in Arizona. With the deadline for complying with the NPOA noise mandate less than a year away (April 2008), the two sides of the issue still have yet to agree fully on the exact meaning of “substantial” and “natural quiet,” much less on means to satisfy the mandate.

The Grand Canyon Working Group (GCWG), a subcommittee of the National Parks Overflight Advisory Group, met in Phoenix late last year primarily to address the matter of whether to ban all daytime flights at and above FL180 in a polygon-shaped 1,000-sq-mi piece of airspace above the heart of the Grand Canyon.

The NPOA was first believed to apply only to Canyon air tours, which routinely fly below 10,000 feet msl. However, a lawsuit filed by the NPS on behalf of environmentalist groups resulted in a 2002 court decision interpreted to imply that noise on the surface of Grand Canyon National Park must be measured from all aircraft at all altitudes.

The latest GCWG meeting devoted the first of its two days to hearing and discussing the results of a Mitre study on the impact of rerouting all flights at FL180 and higher. The study, requested by environmentalists on the working group, concluded that such redrawing of jet airways, if done without full restructuring of the National Airspace System, would have “several operational consequences,” including an increased number of aircraft in adjacent ATC sectors, higher controller workload and reduced lateral and in-trail separation to near-conflict distances.

The study gave a “conservative estimated user cost of $30 million annually if all traffic above FL180 is restricted from the polygon” and warned that “additional user cost factors could triple estimates.”

One of the environmentalist members of the working group accused the Mitre team of deliberately creating routes that would impose the greatest distance increases to maximize estimated higher direct operating costs. A team spokesman replied that mitigating perceived ground level noise within the protected area would require placing the rerouted airways well beyond the boundaries of the polygon.

To date the issue of high-altitude Grand Canyon overflights remains unresolved. After the September meeting, the working group agreed not to discuss
the issue, preferring instead to concentrate on flights below FL180.

Since the NPOA was enacted, the two sides–operators and environmental groups– have become polarized. It has become clear that environmental organizations such as the Sierra Club and its allies would prefer that there be no Grand Canyon overflights.

Recognizing that this goal is unattainable, environmentalist groups have sought to restrict the number and routing of Canyon air tours as much as possible while seeking to expand the NPOA’s scope to include as much of aviation as possible.
The air-tour operators are committed to remaining in business.