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?