It weighs 93g and is made of tyvek, polystyrene and carbon fiber.

In comparison a Canadian Goose featuring in bird strikes weighs in at 2.5 - 6.5kg and is made of organic matter.

I think the risks are small.

The Dropion (+high-altitude balloon) was a "registered flight" so the air traffic control (or, specifically, Urad pro civilni letectvi) knew about this experiment. And then the seeds falling dow are really slow and light.

I was looking into that a while ago. There are multiple categories based on balloon size, weight of equipment. They are mostly concerned and the strength of the string between them.

Away from airports, the smallest balloons as completely unregulated, bigger ones need to be reported. Even bigger ones need a schedule. My overall impression was that all the rules were reasonable amateur-friendly.

Engine engineers usually chuck frozen turkeys into the engine and they do just fine…