Amazon.com has been granted a new patent by the U.S. Patent and Trademark Office for a delivery drone that can respond to human gestures.

The concept is part of Amazon's goal to develop a fleet of unmanned aerial vehicles that can get packages to customers in 30 minutes or less. Issued earlier this week, the patent may help Amazon grapple with how flying robots might interact with human bystanders and customers waiting on their doorsteps.

Depending on a person's gestures — a welcoming thumbs up, shouting or frantic arm waving — the drone can adjust its behavior, according to the patent. The machine could release the package it's carrying, alter its flight path to avoid crashing, ask humans a question or abort the delivery, the patent says.

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