A woman has given birth on an Air New Zealand flight from Auckland to New Plymouth, RNZ understands.

An Air New Zealand spokesperson said after flight NZ5041 landed in New Plymouth on Wednesday one customer remained on board to receive medical attention.

A passenger at the airport said an ambulance could be seen on the tarmac following the plane's arrival.

The passenger said they were later told by Air New Zealand staff that a woman had gone into labour after the plane landed and the baby was born shortly after.

St John and New Plymouth Airport's Fire Rescue team both said they responded to the medical callout around 3pm.

"One ambulance attended and two patients were transported to Taranaki Base Hospital in a moderate condition," a St John spokesperson said.

Air New Zealand said its crew and other customers onboard acted quickly and showed "real manaakitanga".

"We thank everyone who helped and wish the customer well."

Air New Zealand said the subsequent flight to Auckland NZ5052 was cancelled as a result.

The airline said it put on a "recovery service" Wednesday evening to accommodate customers.

-RNZ