Here is my take, having been to the Canyon three times in the last ten
years...

- Ban all private vehicles, as is done in Denali. Air pollution is at an
all time high in national parks such as Yellowstone, GC, Yosemite. Why
is the no-aircraft noise group not up in arms about the harmful
chemical pollution of the air in our national parks?
- The park service just opened more permits for rafters through the
canyon. Given the delicate sites on the river, permits should have
been decreased, using the logic of the no-noise supporters.
- Who is funding the anti-aircraft noise drive? Follow the money.
The outfitters and campgrounds surrounding the park, most likely.
The air charter flights are based miles away, they don't contribute to
the local economy.