He said they were "very grateful" to Air Chathams for stepping in without any obvious support from Air New Zealand.
The airline has also upset Whanganui accounts administrator John McCall who earlier this year booked a holiday in Rarotonga for August.
He found out about Air New Zealand's withdrawal from Whanganui at the end of July through the media.
"We have yet to receive a courteous letter/email from Air NZ apologising for this - that is simply basic PR and courtesy," he said, adding that the airline deserved all the negative feedback.
"Their handling of the Whanganui flight schedule has been incredibly inept and arrogant."
When he contacted the airline, he was told they could either fly from Palmerston North or get a refund.
"When we mentioned the additional cost of flying from Palmerston North we were told not to complain as Air NZ was giving us the flight for the same price. How generous!
"We were spoken to as if it was our fault we had to re-book, and we were pressured to make a decision immediately or we could lose our tentative flights out of and back to Palmerston North - no offer to hold the seats for 24 hours."
Mr McCall has gone with Air Chathams which takes over the Whanganui-Auckland route on August 1.
"We have a very tight flight transfer at Auckland both ways. Air Chathams have been extremely helpful in advising us how to speed up that process - Air NZ could learn a lot from Air Chathams about basic customer service."
Mr McCall said it seemed Air New Zealand had set up the Whanganui schedule to fail.
"This service was always going to be marginal but at no time has Air NZ marketed the new service to point out the benefits of flying from Whanganui instead of Palmerston North, nor did they bring to our attention that seat numbers were down this year and to remind us to 'use it or lose it'.
"Our national airline has not displayed the professionalism it should have no difficulty carrying out."