I've done daytrips to the Grand Canyon--twice--and I really wouldn't recommend it. Possibly if you will never ever be in this part of the world ever again. But otherwise, staying in Flag or closer the night before will make a HUGE difference.

I've also looked into flights. If money is no object, then it may work for you. From what I remember, the flight leaves from the Scottsdale airport (north Scottsdale, Greenway/Scottsdale Rd area), and fly to the Grand Canyon airport. I just couldn't find a car rental at the Grand Canyon to make it work...not sure if that has changed.

One thing I'd highly suggest for a short trip is to enter and exit via different gates. On my 2nd one-day trip, we left the Phoenix area around 8am, grabbed breakfast enroute, stopped in Flag for sandwiches, drove in via Cameron through the East entrance, and ate at a viewpoint near there. Hardly anyone uses the East Entrance, so lines are minimal, and the viewpoints in that part of the park are pretty easy to access (parking isn't bad). We then drove westbound, with our last stop near the El Tovar, which is simply a mess (parking near the village is a PITA). We left via the main exit, drove back to Flag, ate dinner, before the drive back to the Phoenix area.