When drones buzzing over the runway forced London's busy Gatwick Airport to shut down, many travelers wondered why it's so hard for authorities to stop such intruders.
Shoot them down, some said. Jam their signals, others suggested.
Experts say it's not that easy.
Britain and the U.S. prohibit drones from being flown too high or too close to airports and other aircraft. In Britain, it is a crime punishable by up to five years in prison.
Still, there is little to stop a drone operator bent on disrupting air traffic, which British officials say was the case with the Gatwick incident that began Wednesday evening.
The number of close calls between drones and aircraft has increased dramatically in recent years as the popularity of drones has soared. Basic models for amateurs sell for under $100; larger, more sophisticated ones can cost hundreds more.
Britain had 120 reports of close encounters in 2018, up from 93 last year. In 2014, there were six, according to the U.K. Airprox Board, which catalogs air safety incidents.
In the United States, there were nearly 2,300 drone sightings at airports in the year ending June 30, according to Federal Aviation Administration records. Runways have been temporarily closed, but an FAA spokesman said he could not recall drones ever leading to the shutdown of a U.S. airport.