Very strange structure in mountains filmed from plane.

strange structure in mountains filmed from plane going from Portland to Las Vegas. Can someone PLEASE tell THE HELL IS IT!? A top secret military base? An underground bunker? A . landing strip? Natural phenomena? Rebel base on Hoth? OK, to try and answer some of the questions in the was filmed in 2004 and as far as I know was about an hour into the flight and I had been up all night drinking. I’m Scottish so I don’t know flight patterns etc between Portland and Nevada or gener