It's increasing weekly flights between Christchurch and Melbourne from seven to 12, and weekly flights between Christchurch and Brisbane from seven to at least 10.
Weekly flights between Wellington and Melbourne will also increase from seven to 10 over the busier summer period.
It will equate to an additional 260-thousand seats a year on trans-Tasman routes.
The changes represent an almost 50-percent increase in capacity, and a seven-percent increase for Qantas's broader trans-Tasman network.