I love looking out the window when I fly, so curious to know if there are any commercial flights that provide a view of the Grand Canyon.
It's not hard to identify flights which may fly over the Grand Canyon— but finding out which ones definitely will, and whether or not you will have a view if you take one, are a different story.
With some trial and error, you can find flights that pass over the area on any of the websites that offer flight tracking, like FlightAware.com. Grand Canyon National Park is labeled on the "Aviation Sectional" map view, and its contours are visible on that view as well as the "Earth View." Since FlightAware and similar services show the actual reported flight paths of aircraft, they are more reliable for discovery than, for example, tools like the Great Circle Mapper, which rely on purely mathematical calculations.
The Live Flight Tracker shows aircraft currently reports in an area, though this will include many non-commercial flights. As there is a good amount of traffic through this area headed to and from Southern California or Phoenix, you can try plugging in city pairs like MSP-LAX, SLC-PHX, or SEA-TUS in the "Flight Finder" for some ideas.
There is a great deal of variation in actual flight paths, however. Flight plans take into account the winds and the weather, and flights are subject to rerouting by the air traffic control system. Consider that on 25 September 2014, United 1041 DEN-SNA passed straight over the eastern Grand Canyon, but today, the very same flight flies well to the northwest, bypassing it entirely.
Even if you had been on the 25 September flight, you might not have had much of a view. There could have been clouds; or the plane might have been turning, banking your side of the plane towards the sky; or you may have passed at an angle that showed only a vague gap on the horizon, and not any view into the canyon itself. But most importantly, of course, you'd have been flying through the area after sunset.
While approaches to airports are somewhat more predictable— airports have certain prevailing wind patterns and certain preferred runways— the path an aircraft will take over such a large area is much less certain. If you're really excited about the idea of flying over the Grand Canyon, I suggest you look into booking an air tour. Otherwise, enjoy the flight as best you can, and think of any Grand Canyon sightings as a nice bonus.