Air New Zealand has axed its Whanganui to Auckland and Blenheim to Christchurch regional routes, citing a lack of passenger demand.

The airline says the services weren't filling the 50-seat aircrafts, despite their continued efforts alongside local stakeholders.

The two services will no longer be available from July 31.

General manager of networks Richard Thomson says they took a chance on Whanganui at the time, working with the local community to stimulate demand. They even halved the route fare.

"Unfortunately the market dynamics have changed markedly since then as a result of competition entering nearby Palmerston North just 70km away.

"The greater number of destinations, higher frequency of service and wider range of connecting options on offer at the neighbouring airport have unfortunately served to undermine demand of Whanganui services."

Air NZ also says their Blenheim and Christchurch route was a "loss-making service".

But Blenheim's services to Auckland and Wellington will be strengthening in the coming year, with the airline promising more frequency and 35,000 additional seats on its FY17 flight.

Customers booked to travel on the routes planned to drop on July 31 will be offered the choice of a full refund or travelling via another airport.

The regional networks went under review in November 2014.

The airline has also adjusted a number of its regional schedules:

Newshub.