think the plane would be too low for it to be much of a fog deck... Possibly a low ceiling over a power plant or paper mill (both things that tend to be out in the sticks without much else around).
The plane is probably at an altitude of a thousand feet or more, possibly on approach for landing (flaps on wing are extended). Note the lack of any other significant structures or land forms poking out of the deck... which leads me to think that it's a low cloud deck rather than groundhugging fog.