for people. police will be working with the authorities in order to bring this to a close so people can actually be able to get on and to the travel that they were expecting during the christmas period. >> kitty logan is following this story from london. >> this is all still a mystery, 700 flights are due to take off from the airport today but some passengers will be still affected by the backlog for some time to come. it all started on wednesday evening. flights were stopped when a drone was spotted flying over the runway or close to the runway area. police now believe this was intentional but authorities still don't know who is behind this. >> police are following a number of leads. we don't know if this is a single individual with a grudge of some sort or whether a group of some sort. could be an environmental group. no one has claimed responsibility. >> that is little comfort to the hundreds of thousands of