"drones are used to do what most in the industry call the three Ds: dull, dirty and dangerous.The…"

“drones are used to do what most in the industry call the three Ds: dull, dirty and dangerous.
The “dull” part covers missions like border surveillance and maritime patrols that need eyes in the sky for hours at a time. “Dirty” is much more open to interpretation, but the “dangerous” part is clearly defined as when a pilot in a similar mission could become a casualty.”

- Read on CNN.