"Our success is very much due to the support and commitment of the Whanganui community from the beginning and the continued support and loyalty shown over time.
"Whanganui has become like a second home for us so we are really proud to bring our newest and biggest aircraft into the region over winter."
The ATR flights to Whanganui will start on June 7 with a 3pm departure from Auckland.
For the next few months, Friday afternoon and evening flights, Saturday's 8am flight departing from Whanganui, all Sunday flights and the 6.45am departure on Monday to Auckland will use the larger plane.
The ATR charter flights will resume in September.
Mayor Hamish McDouall said Air Chathams had serviced the community well since it took over the Whanganui-Auckland route.
"With an increase in Whanganui's population and the interest we are getting from the rest of the country I am not surprised that an ATR72 has been added to their fleet to assist with greater passenger demand," McDouall said.
"Air Chathams helps maintain Whanganui's relationship with our biggest city, whether that be for work, to visit friends and family, or as a gateway for international travel."