As someone who is flying in the fog himself, I can actually say that getting kills from it is not that impossible - usually it simply forces me to either fly at about 15m (which is enough to see targets in advance; fog blocks your horizontal vision way more than vertical/diagonal vision below certain altitude) or do the blind bombing. If I see the flag area blinking, I will be more than happy to send some bombs that way without actually seeing the target. If I'm in certain plane types, I will also drop spot flares, which show nearby enemies on the minimap long enough for me to make a turn and bomb the living hell out of them.
About snipers, the thing is, I suspect that a certain quirk from BF4 found its way into Battlefield 1 - in BF4, smoke becomes more see-through when you look at it through something with magnifying power (like a scope). I suspect that it's the same with fog in BF1.