[Cementjungle]

Terrorists will take note, and start using drones to take out passenger aircraft. Someone bent on an attack might have been able to guide the drone into the aircraft. Heck, maybe this was a dry run...

Another huge worry is the use of drones to deliver anthrax or dirty bomb materials into a crowded city, or to deliver poisons into water reservoirs, or to deliver explosives to start fires in forests or cities.

[JimSEA]

An anthrax aerosol in a crowded street scene would spread more terror than a dirty bomb. Likely it would be more effective.