Air tour operators at the Grand Canyon would be able to take more visitors over the most popular flight routes under a proposed incentive to make aircraft quieter.
The incentive would apply to the Dragon and Zuni Point corridors, which provide views of the widest and deepest parts of the canyon to the eastern edge. The flights aren't visible from the South Rim where most of the Grand Canyon's 4.5 million visitors travel each year.
Operators use about 3,700 of their assigned flights in the Dragon and Zuni Point corridors from January to March. Those that upgrade aircraft to meet the definition of quiet technology could shift those flight slots to the summer months when demand is higher without losing out on business during the winter months.
"They can kind of manage within their own fleet how they want to do it, but it would give companies credit for truly quieter technology," said Robin Martin, chief of planning and compliance at the Grand Canyon.
Operators don't necessarily have to fly quieter aircraft to win the certification of quiet technology. Under a definition used by the Federal Aviation Administration, some can just add seats to aircraft to qualify.
A provision in the 2012 federal transportation bill to make half of the Grand Canyon free from commercial air tour noise for at least 75 percent of the day requires the Federal Aviation Administration and the Grand Canyon to provide incentives for quiet air technology. Many of the tours originate from Las Vegas.
U.S. Sens. John McCain of Arizona and Harry Reid of Nevada had criticized a proposal by the National Park Service to manage air tour noise at the Grand Canyon and restore natural quiet to the park. The Park Service wanted to make 67 percent of the canyon quiet for three-fourths of the day or longer, but the senators said the noise restrictions were unfair and would decimate air tours.
The first incentive for quiet air technology went into effect in January, reducing fees from $25 to $20 per flight. The FAA later released 1,721 flight allocations that had been abandoned to commercial tour operators for use as long as their active fleets did not increase noise in the park overall.
The public comment period for the latest proposed incentive ends Dec. 10.
Messages left with media representatives for two of the Grand Canyon's largest commercial air tour companies were not immediately returned Monday.
Air tour operators use more than 90 percent of the nearly 45,000 flight slots available to them in the Dragon and Zuni Point corridors, Martin said. About 60 percent of the aircraft conducting tours at the Grand Canyon already meet the quiet air technology standard.
Dick Hinson of the Sierra Club said the impact of the proposal is unclear but could worsen noise levels in the canyon's backcountry where hikers and campers seek solitude. He said the environmental group wants some assurance from the park that it is not going to do the minimum possible in terms of the science.
"It can be a smoke screen," he said. "The incentives should be used to develop engines that are quieter as a source directly."
Martin said the FAA and the Grand Canyon have set a maximum noise level at the park based on flight allocations for 2012. Officials said the new incentive, if implemented, could be discontinued if noise from air tours throughout the park exceeds that level.
"We're looking more at noise than numbers," Martin said.