Three fishermen missing at sea for more than a week have been found alive.

The men, aged 34-61, who appeared to be in good health, were found about 10.30am by the Royal New Zealand Air Force about 550km west of Tarawa, the capital and main atoll of the Pacific Islands nation of Kiribati.

Crew from the Air Force's P-3K2 Orion surveillance aircraft spotted the men waving from their 5m wooden fishing boat about an hour after they began today's search.

Commanding Officer Wing Commander Daniel Hunt said finding the missing fishermen was "satisfying".

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"The last three or four times that we've been up to that area in search and rescue missions we've been successful so it wasn't surprising given the weather conditions ... that we were able to find them."

Hunt said he wasn't surprised that the men were in good health when they were discovered.

"Generally after seven to 10 days, so long as they're still on board their fishing boat, they're usually pretty well off."

Hunt said the RNZAF will stay in the area until a suitable boat is sourced to pick up the men.

"We would maybe do six to 10 rescues a year in that area, it's not regular but it's not irregular."

The Orion plans to drop the men emergency supplies consisting of food, water and a radio and is contacting ships in the area asking them to pick the fishermen up.

"I am pleased that the fishermen were found safe and well and will now be able to return to their families," said air component commander air commodore Darryn Webb.

"I would also like to commend the aircrew as well as those back here in New Zealand who supported the search and rescue mission for a job well done.

"The successful outcome of this mission has demonstrated once again that our air search and rescue capability delivers vital public service both in New Zealand and overseas."

The Orion left Whenuapai on Tuesday morning to search for the missing fishermen. The men were last seen leaving Tarawa on Tuesday last week.

The original search area was about 3500km north of New Zealand and covered more than 33,000sq km. Following the unsuccessful aerial search on Tuesday, the search area was expanded to 55,000sq km.

Fiji's Rescue Coordination Centre, which is responsible for the search area, requested the NZDF's assistance after a two-day aerial search by Kiribati authorities was unsuccessful.

The Kiribati search ship Nakoraoi also helped in the search.

The RNZAF NH90 medium utility helicopters and the P-3K2 Orion surveillance aircraft have flown nearly 180 flying hours on search and rescue missions in New Zealand and the south-west Pacific since January.