When traveling to the US (with American Airlines Brussels-Chicago), I remember crossing Greenland and there was a huge gap in the clouds and 3 huge glaciers, serpenting in the relief were absolutely gorgeous to look at.
Also, flying from Chicago to Las Vegas, I remember the sunset lightings on the canyons (was it Brice or Zion or the Grand Canyon, I'm not sure) and then once the sun had set, there was that milky way on the ground which we approached and it became the colorful Las Vegas. I'm always tired, arriving there, but what a view, what an impression it gives!
And also, looking at the NYC lights, once leaving JFK back for home, and later on, Orion in the sky!
All these flight were in Boeing 767's or 757's.
I also remember taking off, in an helicopter, from the bottom of the Grand Canyon up to the Mile 10 Ranch, above the GC. This was very impressive, flying very close to the cliffs, with the amazing landscape around us; but it only lasted less than 5 minutes.
Yes, I've been annoyed by a neighbour passenger who thought he could stretch his elbows halfway across my seat; yes, I've never been able to sleep in planes...
But what a great view!!!

Raoul