A breach of regulations by Queenstown Airport has been described as disappointing and concerning.
A Jetstar flight left the resort on Saturday at 10.14pm - 14 minutes after the airport's approved operating hours ceased.
Queenstown Lakes Mayor Jim Boult said the incident would be investigated.
''We are very disappointed this has occurred because it is clearly a breach of the agreement and also a breach of trust with residents at Frankton.
''It is something we are concerned about.''
Airport management made him aware of the breach yesterday morning.
Airways New Zealand and Jetstar will also be involved in the investigation.
Mr Boult welcomed the airport's proactive approach.
''It is very clear from its actions, and the airline's actions, they are also taking it seriously. They have undertaken to investigate the matter fully and we expect to be informed of the outcome of that.
''We also expect to hear how they plan to ensure this doesn't happen again.''
Frankton resident Barbara Williams said the breach should not have occurred.
''There is absolutely no reason why the aircraft should have been let go after 10 o'clock. The curfew is set - we only get eight hours in a 24-hour day where we have silence ... that is the only thing it has to do.''
The airport issued an apology to residents, but Ms Williams said that was not enough.
''It really upsets me that it cannot stick to a ruling. It breached its own curfew ... it was its [the airport's] promise. It is taking the absolute mickey out of its own word. It is not good enough.''
The airport's general manager of operations and safety, Mike Clay, agreed.
He supported the concerns raised by the mayor and residents.
''The outcome of this investigation will ensure we have processes in place to make sure this doesn't happen again.
''At the end of the day, a curfew is a curfew and it is not a flexible thing. We don't expect it to be breached.''
He confirmed the aircraft should have departed earlier but was delayed because of snow.
Mr Clay said he would talk to Airways, Jetstar and airport staff today about the situation.
Jetstar put the delay down to weather conditions.
The JQ 220 flight was scheduled to depart for Australia at 8.45pm.
An emailed media statement said: ''The freezing snow conditions in Queenstown on Saturday caused delays to our international services as de-icing of the aircraft was required prior to departure.
"Our pilots received permission to depart Queenstown after the 10pm curfew and the flight to Melbourne was airborne at 10.14pm. We apologise for any inconvenience caused to local residents by the later departure time.''