WELLINGTON, March 11 -- A New Zealand air force P3 Orion aircraft is en route to join the search for the missing Malaysian Airlines flight MH370, New Zealand Prime Minister John Key announced Tuesday.

"The aircraft departed yesterday and, after a stop-off in Darwin, will arrive in Malaysia later today. It is expected to join the multi-national search and rescue mission," Key said in a statement.

"The New Zealand aircraft will be based at the Butterworth air base in Penang along with two Australian P3 planes. They are likely to assist Malaysian authorities by searching the sea areas north of Malaysia," he said.

Two New Zealanders were among the 239 people who were aboard the flight.

"The Malaysian Government has accepted the New Zealand offer to join the international search and rescue effort, and I will be talking to Malaysia's Prime Minister Najib tonight to reinforce that New Zealand stands firmly alongside Malaysia at this challenging time," Key said.

"Much remains unclear about what has happened to the flight. New Zealand wants to do its part in the search and rescue effort to locate the aircraft," said Key.

"While we are aware the hope for positive news is fading, our thoughts remain with the family members of those who were on the flight, particularly the families of New Zealanders Paul Weeks and Ximin Wang," he added.

Auckland Airport, the only New Zealand airport Malaysia Airlines flies to, has beefed up security screening for Malaysia Airlines passengers.

Passengers who flew out of Auckland on a Malaysia Airlines flight on Sunday afternoon had the extra checks, an Auckland Airport spokeswoman said.