A crew aboard a New Zealand fishing boat have hauled in a surprising and gruesome catch: a small plane with a body inside.

Authorities suspect the plane is an aerobatic biplane that was home-assembled from a kit and flown by missing Auckland pilot Daroish Kraidy.

The crew of the San Kawhai was trawling for fish when they brought up the wreckage in the boat's nets, said Trish Sherson, a spokeswoman for fishing company Sanford.

The wreckage was later hoisted aboard a police boat which headed back to Auckland. Police said the plane was severely damaged and that a detailed inspection of it will be carried out on Friday by officials that include a victim identification expert.

Typically, trawl nets are dragged in a wide arc along the ocean floor to ensnare fish. Buoyancy can make it easier to lift heavy objects in the water than on land.

The fishing vessel is one of Sanford's smaller boats and typically catches tarakihi, orange roughy and other fish that live near the coast.

Mr Kraidy's Acro Sport plane is the only plane listed as missing by New Zealand's Civil Aviation Authority. Authority spokesman Mike Richards said the Acro is relatively lightweight and is made with a metal and wood frame that is covered by fabric.

Mr Kraidy, 53, took off on March 25 from Ardmore airfield near Auckland. Minutes later, his plane disappeared from radar screens, leading authorities to conclude he either switched off the plane's transponder or was flying at a very low altitude.

Mr Kraidy had previously flown in the World Precision Flying Championships. His ex-wife and daughter told Fairfax Media in May they believed his disappearance was deliberate after he had battled depression for years.

Fishermen transported the wreckage to a bay near Great Barrier Island, about 56 miles north-east of Auckland, where they met police.

Police said they were in contact with Mr Kraidy's family and friends about the discovery.