Police say an attempt to break into a plane at Kapiti Airport overnight was likely an "idiotic, expensive prank''.
Two flights were cancelled after the attempted beak-in caused the Air Nelson plane's emergency chute to inflate.
Senior Sergeant Alasdair Macmillan of Kapiti police said someone tried to force their way in to the Bombadier Q300's rear emergency exit door between 8pm yesterday and 6am.
"In doing so this has activated an airbag below the door, which is a safety device ... for ensuring the safety of passengers having to exit the plane in an an emergency.''
Mr Macmillan said that frightened off the offenders, "who of course wouldn't be expecting this to inflate - they were just trying to get into the plane''.
A technician from Wellington has been called in to re-pack the emergency chute.
The offenders were not able to enter the 50-seat plane, which was parked on an apron off the airstrip, and no other damage was caused.
Pilots, police and security staff had checked the plane and were confident it had not been otherwise tampered with, Mr Macmillan said.
"There's no rhyme nor reason to it. My supposition is they were just going to see if there was anything they could steal,'' he said.
"It may have been curiosity - it's a stupid, idiotic, expensive prank or adventure that these people or person has attempted, and we'd certainly like to find who's responsible.''
Mr Macmillan said the offenders could have entered anywhere around the terminal, which is surrounded by a high-security fence.
An investigation has been launched involving the police, Air Nelson and Kapiti Coast Airport.
Police called on anyone with knowledge of the attempted break-in to get in touch.
Air Nelson general manager Grant Kerr said the offenders' actions had disrupted the travel plans of 75 people.
Two flights _ NZ8490 from Kapiti to Auckland, and NZ8491 from Auckland to Kapiti _ were cancelled while the aircraft was inspected and cleared for flying.
Flights between Kapiti and Auckland only recently began in October.
"I'm sure the residents of Kapiti are as disappointed as I am that someone would do this so soon after the launch of this new route,'' Mr Kerr said.
The incident follows other airport break-ins over the last 18 months in which people siphoned off aviation fuel from aero club aircraft.
Four people were arrested over that incident.
