Drones have come a long way from being military-grade equipment to commercially accessible toys sold across mainstream stores.

But as well as being disruptive to industries – with Amazon trialing its own drone delivery service – drones have become increasingly disruptive to commercial aircraft, buildings, and people.

Several flights were delayed at a U.K. airport on Sunday after a drone was seen flying close to the runway, raising questions about how disruptive they are, and whether enough has been done to regulate them. The drone caused the closure of Gatwick Airport in southeast England, and meant that four easyJet flights and one British Airways flight had to be diverted.

But the latest near-collision is just one of many drone-related incidents to have caused a stir. Drone-related near-misses with commercial aircraft in the U.S. rose by 46 percent from 2015 to 2016. And a freedom of information (FOI) request released earlier this year revealed that drone-related complaints in the U.K. soared twelvefold in the space of two years.

Unmanned aerial vehicles (UAVs), commonly known as drones, have been causing increasing concern for aviation authorities and experts, following several reported incidents of drones coming within close range of people, high-profile buildings, events, and aircraft.

In 2015, a journalist for the Qatar-based network Al-Jazeera was fined 1,000 euros ($1,137.65) by a French court for flying a drone over central Paris. Tristan Redman was arrested in the Bois de Boulogne park for flying the drone but Al-Jazeera said in a statement that he only wished to “illustrate a piece to camera on domestic drones.”

And last month the head of Portugal’s national airline, TAP, called for all drones in the country to be grounded, following a series of near-misses with commercial aircraft, according to the Associated Press.

“Due to the irresponsible behavior of some — and I’m speaking in a European and global context — (drones) are being used very badly, in a very dangerous way, and that worries us,” TAP Air Portugal President Fernando Pinto said.

The sheer scale of incidents has frustrated airspace authorities, which are left with the task of regulating and enforcing regulation on a technology which is still rapidly developing.

“Flying any kind of drone near an airport or in controlled airspace without the proper permissions is dangerous and unacceptable,” a spokesman for the U.K.’s National Air Traffic Service (NATS) told CNBC in an email on Monday.

“People using drones should apply common sense when deciding where to fly and need to remember that the same legal obligations apply to them as well as any other pilot.”

The U.S. Federal Aviation Administration (FAA) already has drone regulations in place, which mean commercial drones must weigh less than 55 pounds, fly up to a maximum of 400 feet in altitude (at a speed of no more than 100 miles per hour), and can only be operated during daytime hours and up to 30 minutes before sunrise and after sunset.

Under previous FAA rules, all drones being flown commercially had to be registered. But the FAA was hit with a federal court ruling in May, throwing out registration rules which have been in place since 2015. The FAA says it is currently reviewing the U.S. Court of Appeal’s decision.

In the U.K., the Civil Aviation Authority (CAA) holds similar restrictions on the devices, only adding that drones fitted with cameras must not be flown within 164 feet of people, vehicles or buildings, or within 492 feet of congested areas or large gatherings, such as concerts and sports events.

The European Aviation Safety Agency (EASA) has put forward proposals which it hopes will tackle the problem of drone misuse and enforcement. These include requirements for drones to be remotely identifiable, to be fitted with geo-fencing technology which prohibits them from entering out-of-bounds zones like airports and nuclear facilities.

While law enforcement and regulation on drones has proven difficult for authorities, some are looking to raising awareness through education and other means to quell the number of incidents.

The spokesperson for NATS said the air traffic service had launched an app called Drone Assist to show airspace users where they can fly drones safely, and “a joint website with the CAA to promote safe drone flying.” He said NATs was in talks with drone retailers such as Maplin to improve the distribution of safety-related information to drone operators. “We will continue to work with all parties to encourage the safe use of the U.K.’s airspace,” he added.

In the U.S., drone users have been prosecuted for flying drones near a range of buildings and events, from smuggling drugs to prisons to “stalking” protests at the Dakota Access Pipeline. While in the U.K. a man was charged with flying a drone too close to Buckingham Palace, the residence of Queen Elizabeth II. Other arrests of drone operators have been made across the globe.

But some pilots are calling for more to be done. The British Airline Pilots’ Association (BALPA) urged for there to be “better education of users, compulsory registration during which the (existing) rules are made clear and more high profile prosecutions for offenders.”

“Drones can be great fun, and have huge commercial potential, but with a significant increase in near-misses in recent years it seems not everyone who is flying them either know or care about the rules that are in place for good reason,” Steve Landells, flight safety specialist for BALPA, said in a statement on Sunday.

“We believe a collision, particularly with a helicopter, has the potential (to) be catastrophic.”

He added: “Measures should be put in place that will allow the police to identify and locate anyone who flies a drone in an irresponsible way.”

Sussex Police in England has said it is now working with the CAA to find the culprit who flew the drone at Gatwick Airport. “Following reports of a drone sighting at Gatwick Airport at about 6.12 p.m. on Sunday (July 2), police are liaising with the Civil Aviation Authority pending further enquiries,” it told CNBC in an email.