Concerned that explosives concealed inside a UAV could pose a danger to first responders attempting to find its registration number, the FAA now requires owners to display their registration number on an outside surface.

The rule took effect on Feb. 23. When the requirement to register drones was introduced in 2015, the FAA allowed the number to be placed in an enclosed compartment accessible without using tools. This was because many small drones — particularly quadcopters — were considered too small to provide an external surface large enough for the registration number to be readably displayed.

“Subsequently, law enforcement officials and the FAA’s interagency security partners have expressed concerns about the risk a concealed explosive device might pose to first responders upon opening a compartment to find a drone’s registration number,” the agency said.

The FAA “believes this action will enhance safety and security by allowing a person to view the unique identifier directly without handling the drone.”