ANONS today I was on a flight between PNW and TX and I noticed this outside my window. It was exactly halfway through the flight which must have been right around Colorado Springs/Denver though I can't be 100% sure. It looked like a steady plume of smoke coming from an area in the mountains but I didn't see any fire and it didn't look like a forest fire. I know a whole bunch of the DUMBs are in the Colorado/Denver/Colorado Springs area. The smoke was thick enough you could smell it in the plane. It made a reddish smoky layer around the clouds. I happened to be looking out the window at the time and snapped some photos and a short video.
Here is the video and the smoke in the clouds