Grand Canyon and Las Vegas are easily recognized from the air, as are some of the world's tallest mountains.

I've also found it interesting to fly into/out of LA during wildfire season. You really get a better appreciation of how widespread they can be when seen from the air.

One thing I've always wanted to see, but never have, are 4th of July fireworks from the air. This year I flew on the 4th, but it was a daytime flight from DUB to ORD, so no fireworks in sight.