pose a threat - be dangerous or harmful, cause concern - make people worried, public safety - protection of people in general, national security - protection of a country, unidentified objects - things people see but cannot clearly recognise, sightings - events when people see something unusual, authorised - officially allowed, malicious intent - plan to do something bad, versatile - having many uses or applications, remotely - from a distance, without physical contact, rotor - a hub with blades used for movement in air, propeller - a device with blades attached to a motor, hover - stay in one place in the air, onboard - available on a vehicle, ship, or aircraft, pilotless - without a human controlling it, surveillance - continuous observation of a place or people, nimble - agile, able to move quickly and easily, appliances - devices or machines used at home, comeback - a return after a break, artificial - man-made, not natural, peak - the highest point, autonomous - working independently, without control,

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