Monument Valley from the ground is stunning, so from the air it should be err, well, better than stunning! From memory, Page would be a convenient airfield.
What about Yosemite Valley? Not sure if there are restrictions on flying, apart from the natural ones (terrain > 9000 ft).
Another good place is Anza Borrego National Park, between San Diego and Palm Springs. There is an airport in the small town of Borrego Springs and I can recommend a good hotel for an overnight. There is also a great Mexican restaurant (not that they are in short supply in that part of the world).
TG.