An Air New Zealand domestic flight had to land early after a passenger became unwell mid-flight.

An Air New Zealand spokeswoman said flight NZ675 from Auckland to Dunedin was diverted to Christchurch when a passenger became unwell.

The aircraft later continued to Dunedin where it landed at 4.20pm - about two hours and 15 minutes late.

For privacy reasons the airline would not able to elaborate on what happened to the passenger.