You know we all disliked you while you worked on that matte painting. I still like how it turned out though.
Lets go in order though, the first painting… Well the perspective is wrong. The truck in the foremost ground is the part that really doesn’t fit. I am guessing the trucks and plane are one entire element? I would say scoot it(technical term that one) to the right. Also, this is nitpicking, but the sun is in the wrong spot to where the highlight is on the plane and its cast shadow on the mechanical thing(boarding arm? what is that called?). Otherwise the elements themselves look well integrated.
Now for your final… That darn thing. Well I honestly do love it, compositionaly, and elements. Few things, well the first is a question. The god ray, on your banz-… tree, wouldn’t that extend up to the lens flare? From the look of it it stops abruptly at the middle arch. The strong highlight looks too short, it should extend higher for where your sun is. Some of the shadows around the entire composition are too strong(especially in the cracks along the right wall). The wall on the far left closest to viewer, has the wrong shadow color. And I personally I think it and the wall next to it are too dark for the entire composition. No where in your image, does it ever go to total blackness, and for how much light bouncing is happening it should atleast be lit by a red reflected light.
Gotta love that UFO.