Specific, carefully selected helicopter tours, such as over or in the Grand Canyon, Yellowstone or other national parts worldwide should go ahead as planned, by seeing all sights you've paid to see.
One reason why the tour outlined in the flightplan might not go ahead may be due to the weather.
Weather will not often delay or cancel the helicopter tour over top tourist hotspots or national parts; but poor weather, and so poor visibility will prevent you viewing the sights miles away.
If you're seated in the middle seat in the back, its here where views are limited.