A former Stormont department has been censured for failing to monitor the number of late-night flights at George Best Belfast City Airport.
The Northern Ireland Public Services Ombudsman (NIPSO) watchdog found "maladministration" by the former Environment Department and called for its replacement to issue an apology and payment to nearby residents.
More than 3,000 late-night flights took place over a seven-year period.
A planning agreement meant the airport could only operate after 9.30pm in "exceptional circumstances".
Ombudsman Marie Anderson said: "The department had no operational definition of the phrase for the purposes of monitoring compliance with the agreement.
"In response to the ombudsman's inquiries, the department stated that the 3,000-plus late flights which took place over a seven-year period were all 'exceptional'."
The ombudsman investigated a complaint brought on behalf of the group Belfast City Airport Watch Limited (BCAWL), which claimed that no action was being taken by the department in relation to flight arrivals and departures between 21.21 and 23.59.
Mrs Anderson has called on the Department for Infrastructure to issue an apology within one month to the residents' group and make a "consolatory" £1,000 payment.
The ombudsman also said the department failed to gather data on a regular and systematic basis on late-flight movements from 2008 to 2011 for the purpose of monitoring the airport's compliance with the 2008 Planning Agreement.
It said the department failed to investigate BCAWL's complaint thoroughly and provide adequate responses to concerns raised.
BCAWL member Professor Mari Fitzduff said residents were delighted.
"We have spent years trying to convince the authorities that they needed to take action on this issue.
"Our case was dismissed by the department but now, finally, we have been vindicated.
"We hope this will mean that long-suffering residents can finally look forward to peace and quiet in the late evening and night-time.
"What's important now is that the department acts on the report's recommendations as quickly as possible."
An airport spokesman said: "Over the period that the Ombudsman studied, (October 2008 - March 2016), the airport handled 295,629 flights. Those delayed flights between 21:30 and 23: 59 accounted for only 1.04% of all total aircraft movements at the airport.
"No airport in the world operates without delays.
"Belfast City Airport goes further and fines are paid in respect of flights that operate during these hours, with 120 local community and youth projects benefiting from £350,000 which has been dispersed via the airport's award-winning Community Fund."