Chief operating officer Todd Grace said the existing domestic lounge was designed almost 20 years ago and was now cramped at peak times, which discouraged passengers from going through security screening until the last minute.
That led to surges for screening and longer wait times.
The $5 million project included an interior terminal redesign to make the domestic-departure lounge bigger, and upgrading amenities for passengers waiting to board a plane, including incorporating the existing Airspresso cafe into the departure lounge area and increasing the number of toilets.
There would be a separate screening area dedicated to bulk goods, and a new land-side cafe, with outdoor seating in the airport forecourt.
At the same time, some seismic strengthening work would be done, Mr Grace said.
The work meant passengers boarding ATR-72s at gate 1 would need to pass through security screening for about eight weeks.
The upgrade would be done in stages and at night, with the most disruptive stage finished before the winter school holidays, and the project fully completed by spring.
