Someone did fly a sort of balloonocopter, a quad copter that used inflated balloons as the cross arms, My disappointment is immeasurable that they were not allowed to use a lifting gas in it. I mean, it flew poorly anyway, but seeing as it is an unmanned vehicle, I would have used hydrogen as my lifting gas, and then when it had a catastrophic failure it would get a viking funeral for free.

As it is, there were some impressive metal fires during crashes, another win for lithium batteries.