Nelson Airport was forced to shut down on Friday after security staff found a suspicious bag that was making ticking sounds outside the terminal building.
A search of the bag revealed an old alarm clock as the source of the noise.
An elderly man had accidentally left the bag outside the terminal building.
Police are speaking to the man, and say the incident is an example of people not taking proper care of their baggage in public buildings.
The terminal building had to be evacuated for a short time from just after 11am during the incident.