Fezzic: I can't really recognize anything as a tree, never mind which tree
. So I can't judge on the tree issue.
What makes me conclude that it's most likely smoke:
*the next frame shows the smoke dispersing, and it remains for some frames, getting thinner.
*the engine did hit objects, very likely to cause engine damage
*in the alternating image presented in this thread, I do recognize what could be a 757 in front of the smoke. It is not clear enough to really tell, so I'll stick to "could be".
What makes me think that your proposition is less likely, is that we'd have both a glare and smoke. Of course that's possible, but it simply seems more likely to me that both effects are the same thing.
As things are not clear at all, I am not intending to discuss things ad nauseum. Your reasoning is clear and I can't pinpoint any error in it. Same goes (IMO) for mine. SO it boils down to what each person finds most convincing, giving the vague nature of the footage.