A Royal New Zealand Air Force Orion is flying to Kiribati to join the search for three fishermen missing for more than five days.
The Orion, which specialises in open ocean searches, left Auckland on Saturday at 4.30am and is expected to arrive over Kiribati later in the morning.
The men, aged 25, 27 and 30, left Betio Island, South Tarawa, in their 4.5 wooden boat for a day's fishing on Monday.
They had 56 litres of fuel, a bucket of water and 20 buns.
Fiji's Rescue Coordination Centre requested the Orion's help after a local search failed to find them.
The search area encompasses 34,300 square kilometres, says Air Commodore Darryn Webb.
Orions have been used in seven Pacific search and rescue missions so far this year.