Passenger accounts varied: some felt the plane had plunged, others that it had climbed sharply.
One passenger, Deborah Sylvester, 34, said it felt like the steep run on a rollercoaster. "It was very sudden.
"You got that feeling where you lost your stomach. I closed my eyes and hoped for the best.''
Her husband Andrew Sylvester said the plane throttled suddenly out towards the sea for about six seconds.
"The wife absolutely freaked. Everyone was looking at each other. No one was sure what was going on.''
The Airbus climbed 1000 feet to allow adequate distance between it and the smaller plane.
Airways NZ spokesman Lew Jenkins said, "It was looking to being a potential safety event.'' Jenkins said yesterday they would start their investigation into the event.
A CAA spokesperson said all airline aircraft are fitted with equipment which detects the position of other planes via radio transmissions.
Known as Traffic Alert and Collision Avoidance (TCAS), the system alerts pilots if their plane comes within six miles (9.6 kilometres) of another aircraft.
If the system senses another aircraft it audibly warns the pilot and suggests a course of action.
CAA said TCAS alerts were infrequent, and on average the CAA receives about 100 to 150 alerts a year.
