The rescue helicopter crew who flew to the scene of a light plane crash in the Southern Alps believe that crash was "unsurvivable".

Senior pilot Stu Farquhar at Canterbury Westpac Rescue Helicopters told the NZ Herald that after speaking to the crew "it was obvious from the wreckage site that there were no survivors".

The light plane, with one person onboard, was reported overdue on Thursday at 11am after it took off from Franz Josef at 9am heading for Rangiora.

McCoy Glacier location. Image / Supplied

The Canterbury Westpac Rescue Helicopter located the aircraft, in poor weather conditions, near Mt Nicholson, on snow at McCoy Glacier, on the eastern side of the Southern Alps.

Farquhar said "It was a very broken aircraft".

"The aircraft was whole but in pieces on the ground. They weren't strewn across a large area, it was just all the bits were in one place," he added.

Canterbury Westpac Rescue Helicopter. Photo / Supplied

Strong northwesterly winds buffered the helicopter as it made its way to the crash scene.

"The weather conditions were such that the snow and cloud looked like a "white out".

The helicopter set down in a sheltered valley and used the track of the aircraft on Flight Radar, the emergency locator, and GPS coordinates, to locate the aircraft.

"They did hover over [the plane] for a period of time to take photos and have a good look at the scene to confirm from the air that it was unlikely to be a survivable accident", said Farquhar.

McCoy Glacier on the estern side of the in the Southern Alps. Photo / Topomap

The Rescue Coordination Centre's attempts to get the Alpine Cliff Rescue team to the site have been put on hold due to deteriorating weather.

An RNZAF NH90 helicopter has been sent to Christchurch to assist with the operation.

RCC said that an attempt will be made to reach the location of the crash when the weather improves.