Humans probably shouldn't. It might be their weakness that they have very little variety the air, just dragon knights and ornithopters. Scalefolk have dragons in plenty, and elves have their dragons plus the idea for eagle riders. I think orcs and dwarves are the only ones with airships.
It should be noted that dwarves are smart enough to use helium or hot air, as opposed to hydrogen. They don't want to get blown up i guess.