I would expect them not to fly into any kind of structure. That they'd hit a crane is pretty insane considering what the results of something like that could be.
You are setting an impossible standard.
Drones are lightweight, they're not going to do much to heavy machinery. Basically the same as a brick wall.
The real fear is propellers hitting a human. The result is not good at all.
The impact would be quite serious, if they crash at speed but even falling on a car or a human would be quite serious, possibly deadly, even if the propellers don't spin.
Maybe if they fly at much higher altitudes for most of the flight.