I don't know how the FAA has set the flight restrictions over the Canyon since I left, but here's what I've been able to find out.
The only flights allowed below rim level and only at certain flight levels (IE, rotary wing at 6000' MSL, fixed wing at 7000' and don't quote those altitudes. They were used for explanation purposes only) are pre-determined tour flights and only on designated flight paths that were previously set up with the FAA and NPS. GA and transient aircraft must fly only in certain "corridors" and at a flight level well above the tour routes.
I lost 3 close friends who were very good pilots in that crash in 1986. One of which was my CFI. Those of us who knew these pilots have come up with what appears to be a legitimate cause, but without formal declaration of a cause, we'll never know if we were right or not. After this accident, the NTSB and FAA adjusted the flight levels for the two types of tour aircraft and scrunched more aircraft into a smaller airspace. Recipe for disaster, IMHO, but they did it anyway. There was never a cause officially determined by the FAA and NTSB last I have heard of. The flights to the bottom usually are designated only for maintenance to park equipment (I flew with my father many times to the bottom and fished in the Colorado or Bright Angel Creek while he fixed the telephone systems for the NPS) and river rafting support flights.
The website that was previously mentioned about the
Grand Canyon airspace is very informative and does show the adjusted flight levels that were incorporated after the 1986 accident. Thanks for that link, by the way.
I forgot to mention that any tours you may take over the Canyon with one of the commercial tour companies is a tour worth taking. The view and sights are unbelievable and I never tired of taking those space-available flights that were available to local residents. With the right pilot and on the right helicopter tour, you'll nose in to the cliffs and see cliff dwellings, fly
through a couple of rock formations and generally have the time of your life!