Dozens of passengers packed Palmerston North Airport after an ATR 72 aircraft was forced to make an emergency landing this afternoon, with 71 passengers onboard.

Air New Zealand flight NZ5075, en route to Nelson from Auckland, was diverted to Palmerston North after encountering problems with its nose landing gear.

All flights in and out of Palmerston North have since been cancelled tonight, with affected passengers being bused to Wellington.

Customers booked to travel on those services can call the Air New Zealand Contact Centre on 0800 737 000 to rebook on an alternative service.

In light of the circumstances, Air New Zealand is also offering full fare refunds, regardless of the fare type purchased.

Emergency services were onsite at Palmerston North airport this afternoon in case the aircraft did have problems when landing.

The plane was diverted into a holding pattern, and circled above the airport for close to an hour.

The aircraft will remain on the runway tonight until it has been inspected by engineers.

Air New Zealand said pilots followed standard operating procedures and requested emergency services be on standby for the landing.

Cameron Death, who was waiting at Palmerston North airport for a flight, said everyone was cleared off an Air New Zealand flight due to leave for Christchurch.

He said the passengers were told that because of the emergency with the other plane, they needed them off the runway.

Mr Death said there was "a lot of smoke" when the plane landed, but that was it.