After debating Grand Canyon air-tour noise for eight years, the Grand Canyon Working Group (GCWG) has left the issue to the National Park Service (NPS), which often supports environmentalist positions. At a recent meeting the GCWG disagreed on NPS alternatives, including a seasonal shift in air-tour corridors by alternatively closing the Zuni and Dragon corridors, which are now open concurrently. The GCWG adjourned indefinitely, leaving NPS to develop a single alternative. “The FAA does not have a role at this point,” said Lucy Moore, the GCWG mediation facilitator. “When the NPS presents one preferred alternative, the FAA will then review it for safety issues.” Last September, the NPS adopted a proposal that clarified “substantial restoration of natural quiet” at Grand Canyon National Park. In the rule, the agency said it would achieve substantial restoration of natural quiet when the reduction of noise from aircraft operations at or below 17,999 feet msl results in 50 percent or more of the park achieving restoration of the natural quiet (no aircraft audible) for 75 percent to 100 percent of the day, every day. NPS said that 50 percent of the park is a minimum in the restoration goal.