It's only a matter of time

:Before one or more drones get sucked into a passenger plane's engine while it is taking off or landing.

The best example of a successful end to something like this is "Sully" Sullenberger who landed his plane without any engines into the Hudson River and everyone survived because of a bird strike to both engines at once.

However, a drone (because it has metal parts or at least batteries and plastic and silicon chips and stuff like that) it might cause  more problems of new kinds than the flesh, bone and feathers would of birds hitting engines and shutting them down.

So, testing small drones flying into plane engines or cockpit windows or wings might be important to the well being of at first hundreds of people, then thousands, then millions.