Air New Zealand is adding 145 flights between Auckland and Napier from January to March.
The move follows the withdrawal of rival Jetstar's regional services.
Air NZ said on Tuesday it would add the additional flights, a total of 9172 seats between Auckland and Napier, to its schedule at the start of 2020.
The flights are included in the 586 additional one-way flights expected to be operated by the airline.
The other destinations included in the additional flights are Auckland to New Plymouth, Nelson and Palmerston North, as well as between Nelson and Wellington.
Air New Zealand Acting Chief Executive Officer Jeff McDowall said the airline had been working hard to look at how best to utilise its turboprop aircraft and crew to support routes impacted by Jetstar's withdrawal.
"We're pleased to be able to get behind regional New Zealand by adding these extra services, particularly during the summer months.
"These additional services reflect an increase of nearly 50,000 extra seats to and from regional New Zealand from December through to the end of March."
The airline also announced late last month it will be adding an extra 253 one-way services on the same routes in December, reflecting an increase of more than 15,500 extra seats in that month alone.
Air New Zealand is also assisting affected Jetstar customers with a special fare.
Eligible customers can email firstname.lastname@example.org with proof of their affected Jetstar ticket.