The New Zealand Defence Force has launched a search for a fisherman missing off Tonga since Saturday evening.
His boat broke down off Tongatapu, the main island, and he hasn't been heard from since he called his family on Saturday.
Searches so far have failed to find him, so the Defence Force sent the P-3K2 Orion aircraft to help.
It left Whenuapai Airbase in Auckland on Monday afternoon and is expected to arrive at around 4:45pm.
"The crew will try to find the vessel and establish communications with the skipper so we can ascertain the problem and provide assistance as required," Air Commodore Darryn Webb said.
"Tongan authorities have launched a search but have had no success to date."
The boat is thought to be between the islands Tongatapu and Eua, a search area of around 16,600 square kilometres.