BBC News says 15,000 in 3 years Noise complaints soar at London Luton Airport - BBC News and "Just 20 people were behind 72% of complaints while almost half of all complaints (6,700) came from the same five residents in Harpenden"
Then "Complaints rose from 441 in 2015, to 1,024 in 2016 and 1,485 in 2017 and campaigners said they had "not seen any changes" in noise reduction. " so I think this is number of single individuals?
Nothing new in that. Back in the early 90s when I worked for a LTN-based airline, I was in a meeting with our MD and an official from the D of T (or whatever that week's name was.) The latter threw in that the previous year had produced 600 or so (can't remember the exact number from 25 years back) noise complaints; short pause; "of which all but about 40 were from the same resident of Harpenden." The total was certainly way above the 441 quoted for 2015.