Image copyrightGetty ImagesImage caption Anti-drone equipment was deployed by RAF at Gatwick until this week Gatwick and Heathrow are to spend millions of pounds on anti-drone technology following disruption at Sussex airport before Christmas.The equipment, which can detect and jam communications between a drone and its operator, was deployed by RAF on a roof at Gatwick last month.About 1,000 flights were cancelled over three days due to drone sightings.Gatwick said it had spent £5m to prevent future attacks, and Heathrow confirmed it would be buying systems.More than 140,000 passengers at Gatwick were affected during 36 hours of chaos between 19 and 21 December.The military was brought in by government and was only stood down on Wednesday this week.The Ministry of Defence said personnel from Royal Air Force Regiment were involved in deployment.Last year it was reported that MoD had ordered Drone Dome system developed by Israeli company Rafael.

The system has a range of several miles and uses four radars to give 360-degree detection to identify and track drones.However, it is understood MoD is still waiting to receive system and alternative technology was in use at Gatwick.Image copyrightGetty ImagesImage caption Thousands of passengers were disrupted by drone incidents at Gatwick before Christmas Gatwick and Heathrow have not disclosed equipment they plan to use in future.A Gatwick spokeswoman confirmed airport had invested in new anti-drone defences after disruption.A spokesman for Heathrow said: "The safety of our passengers and colleagues remains our top priority."Working closely with relevant authorities including Met Police, we are constantly looking at best technologies that help remove threat of drones."Sussex Police, which is still investigating disruption, says it was caused by "numerous instances of illegal drone activity".The force said it has "relevant sightings" from 115 witnesses - 93 of whom it described as "credible" - including airport staff, police officers and a pilot