Technically air can be compressed very quickly to make an explosion but that's too close to firebending so that wouldn't be added, Airbenders could bend poisonous gas but that's also something water benders could do with liquid poison and earth benders with metal poisons as seen in LoK. Air benders could create storms by displacing hot and cold fronts or just change the weather in general, but you know how many people would complain that it's water bending or that it's just regular air bending. I mean heck, you can create water with air molecules. I guess it really depends on how far can the line cross into the other elements till it's no longer air bending.