After a mystery drone nearly collided with an aeroplane as it came in to land at Heathrow in July, there have been further warnings surrounding the threats posed by unmanned air vehicles (UAV).
The UK Airprox Board (UKAB), which oversees air passenger safety, is working on a report confirming the Airbus A320 pilot saw the drone while flying at an altitude of 700ft on July 22.
So what are the risks associated with drone technology?
It isn't always possible for Air Traffic Control - which typically uses a combination of radar, anti-collision warning systems and voice instructions to pilots - to detect drones.
The fact they are becoming more prevalent also means those tools aren't "adequate to cope with the expansion of [drones]", according to a study by the Birmingham Policy Commission.
While some types of military drones "are large enough to be detected on radar, many smaller systems are not", the study said.
This means the rules currently safeguarding against potential collisions are going to become "increasingly difficult to maintain".
The report also warned drones are "a potentially new and useful tool to those of criminal, including terrorist, intent".
It said more must be done to prevent drone technology being used for "malign purposes in the domestic environment".
Drones strapped with explosives would make very "effective terrorist devices", the report said. Their ability to fly past and over obstacles also makes such attacks "particularly difficult to defend against".
Even if buildings are insulated against potential drones attacks "it is entirely possible that in a public space like a shopping centre or sporting stadium, an attack could be launched from within", the Birmingham Policy Commission said.
"Crowds at sporting events or rallies could be vulnerable ... if a future terrorist group were to look for means of dispersing chemical or biological agents," the report said.
"While such a scenario has so far not posed a real danger to UK citizens ... it is a threat that the UK authorities took seriously during the 2012 Olympics."
Additionally, a number of commentors have warned biological terrorism is particularly well suited to unmanned drones because "its flight stability permits the release of [an] agent evenly along a line of contamination".
Unmanned drones do not have the same secure satellite controls and communications which protect aircrafts and operators.
This makes unmanned drones "vulnerable to hacking by third parties who could then commandeer" them and direct them to "malign intent, stealing it or crashing [them]", according to the Birmingham Policy Commission.
Carrying out crime
Criminal gangs could use drone technology to help them carry out a variety of crimes, according to the report.
They could be used to glean information on a particular property or area. For example, smugglers who want to learn more about border control could snoop on anti-smuggling patrols or police movements.
Drone technology can also be used to act as a lookout for "burglars, train robbers and poachers". In a worst-case scenario they can even be manipulated as "instruments of attack, murder and assassination".
Last month, the Lords Internal Market, Infrastructure and Employment Committee was told unmanned drones were "undoubtedly" being used to harass people.
Chief inspector Nick Aldworth, of the Metropolitan Police, raised a number of privacy concerns.
He said the public were vulnerable because if a drone "whizzes past your window and catches something you would rather it didn't catch", it was difficult for the police to track down who was flying it.