London Gatwick briefly halted departures and arrivals on Friday after reports of another drone sighting near the airfield of the second-busiest airport in Britain snarled travel for a third day during one of the busiest travel periods of the year.

The airport had suspended operations on Wednesday after two drones were sighted near its runways. It remained closed on Thursday after more drones were spotted, and the military was called in to help local law enforcement as they struggled to find the operator of what authorities called an "industrial" drone.

Flights began again on Friday but were halted temporarily due to an additional reported drone sighting, the airport said. It has since reopened.

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The incidents underscore how easily a drone can cripple air travel. Air safety regulators have sounded alarms about the threats of drones near aircraft and airfields, as the devices become more popular and easily obtainable.

Government authorities in the U.S. and elsewhere have warned about the dangers of drones potentially colliding with airliners. Researchers at the University of Dayton this summer released video of a test of how a drone could damage an aircraft. The video showed a 2.1-pound DJI Phantom 2 quadcopter .

The incidents at Gatwick "[highlight] the importance of ensuring U.S. national defense and homeland security departments and agencies have the authorities and capabilities necessary to counter threats posed by the unsafe, unauthorized, or malicious use of UAS, whether at airports or anywhere else in the national airspace," U.S. Department of Homeland Security spokeswoman McLaurine Klingler told CNBC on Thursday.