LONDON (BLOOMBERG) - The disruption to hundreds of flights at London's Gatwick airport after it was buzzed by miniature drones shows just how easy it can be to disrupt advanced aviation networks with simple, inexpensive devices.
Airports have been raided by drones before. Dubai International was briefly closed in 2016, and Wellington, New Zealand's main hub, was shuttered for 30 minutes this year when a mystery craft was spotted close to the runway.
But as thousands of travellers at Britain's second-busiest airport try desperately to salvage their holiday plans, the incident reveals how tough it is for the authorities to combat the problem created by this game-changing form of aviation technology.
As of Friday (Dec 21) morning, a limited number of aircraft are scheduled for departure and arrival, more than 30 hours after the drone sightings first shut down commercial flights.
While airfield operators around the world have been girding for more drone disruptions and safety issues, the length and severity of the chaos at Gatwick is a stunning eye-opener, said Mr Christopher Oswald, vice-president for safety and regulatory affairs at the Airports Council International, a trade group in North America.
"It just represents all of these very thorny challenges, which Gatwick does really bring into very stark relief," he said.
The law already is clear in most jurisdictions and penalties for violation can be severe. In Britain, drones are not allowed to fly within 1km of airports and cannot climb above 400 feet (122m), to avoid conflict with flight paths.
Aviation Minister Liz Sugg said the operators of the Gatwick craft could face five-year jail terms if caught.
That is a big "if".
Modern airports rival the size of some cities, making their perimeters almost impossible to permanently police. And surrounding buildings offer almost limitless opportunities for drone operators to hide while maintaining line-of-sight control of their troublesome devices.
The latest drone technology adds a new dimension. Relatively affordable unmanned devices can be flown miles away from an operator using remote video that shows the equivalent of a plane's cockpit view.
British police said the Gatwick incursions were clearly deliberate, as the drones variously appeared, vanished and then emerged again from Wednesday night through most of Thursday. That could shift attention from how best to regulate drone flights to practical ways of neutralising the threat and finding scofflaws.
United States law enforcement and homeland security agencies are drafting standards that would require all but the tiniest drones to broadcast their identity and position so the authorities can identify operators who have crossed the line.
The Federal Bureau of Investigation and other agencies blocked aviation regulators from moving ahead two years ago with rules allowing more unmanned flights over crowds until the authorities could move ahead to address security concerns.
Another mechanism that may help is geofencing. Drone makers including China's DZ DJI Technology use built-in Global Positioning System (GPS) to alert a pilot who is about to fly into restricted skies, such as around airports and prisons. But such systems have vulnerabilities, according to researchers. And they raise even more vexing legal and political issues.
Tracking technology works for lawful operators who blunder into the wrong place, but criminals may subvert such efforts. Similarly, GPS limitations would not stop deliberate attempts to interfere with flights.
The US Federal Aviation Administration last year advised airports not to experiment with the growing number of anti-drone products because the agency had not had a chance to vet them. And solutions such as jamming radio signals could create safety problems by interfering with existing aviation radio systems.
Some technologies are illegal. The US Federal Communications Commission prohibits broadcasting on frequencies used by other devices, and there are questions about whether tracking a drone's radio signal could be considered prohibited wiretapping.
"There won't be a silver bullet," said Dr Randy Villahermosa, executive director of innovation at Aerospace Corp, a federally funded research organisation in the US.
"It will be a constant cat-and-mouse game. You'll always have to think in layers of defence in order to ensure that you have some effective means of countering the threat."
Unlike the aviation safety and security issues of the past, addressing errant drones is more like battling hacking, said Dr Villahermosa, whose organisation has tested anti-drone technology.
There are many remedies - and proposals get pretty creative. Dutch police in 2016 proposed using trained raptors to take out rogue devices, a variation on employing hawks to scare birds from runways. A study funded by the US Air Force and conducted by researchers at the University of Oxford suggested using peregrine falcons, which in their natural element kill their quarry by colliding with them.
Colorado-based Liteye Systems has developed a system that uses radio signals to halt a drone and force it to land, while Australia-based DroneShield is developing a device resembling a traditional ballistic weapon. Police in Japan have experimented with snagging target objects mid-flight using a net deployed from an even larger drone.