It seems there was a rash of "drone incursions" into airport areas in England in the past year. A special group called "Airprox Reality Check" was set up to investigate the reported sightings to help find perpetrators. Well, it seems that just about any unidentified anything became a drone around English airports. So far, they can not collaborate a single incident as factual.
Link takes you to the explanation of the organization & it's findings: