It's a hexacopter (or drone, whatever you feel most comfortable with), so it will be much safer than quadcopter or helicopter due to propeller redundancy (depending on the weight, 2 can fail and still fly normally)... although, the hydrogen fuel cells are still on its birth... in terms of safety. It's true that "their" usage is environmentally safe, because of the high usage of water as output transformation (around 95% as they claim), but on the other hand... it's basically a BOMB! Crashing one on the ground... will be certain death. Unless they found a way to inert the battery before it gets "compressed" enough, blowing when hydrogen gets released into normal pressure along with oxygen.