An RNZAF Orion has located a Tongan fishing vessel which had suffered engine failure in the South Pacific.

The aircraft left Auckland's Whenuapai air base at first light on Saturday and found the stricken vessel about 9am.

The six crew aboard the fishing boat had sent a dawn distress call after experiencing engine failure.

Air Component Commander Commodore Darryn Webb said the Orion dropped emergency supplies including a radio, water and food to the boat.

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"It's always pleasing to successfully locate those in distress in any search-and-rescue mission," Webb said.

"Although the vessel appears to have communication difficulties, the crew reported that the two men they spotted on board were safe and well," Webb said.

The cruise ship Albatros​, which was about 185km away, was sailing toward the fishing vessel to assist, he said.