Eric and Kathy Hertz are understood to be within the wreckage of their plane as no bodies were found floating on the surface after Saturday's crash, police revealed this afternoon.
The couple were in their twin-engine Beechcraft Baron when it plunged into the sea on Saturday about 20 kilometres northwest of the entrance to Kawhia Harbour. Debris and an oil slick has been found, but the plane has not.
Today's detail emerged during a combined press conference from Waikato Road Policing manager Inspector Marcus Lynam and warrant officer James Harper of the Royal New Zealand Navy's Mine Countermeasures team.
Lynam said under the crash circumstances, they would expect to find any bodies on the surface.
"We did an extensive search on the day and nobody was located on the surface of the ocean," he said.
The pair told media they were still in the search phase and had not yet located the remains of the 2degrees mobile phone company chief executive's plane.
Lynam and Harper could not say whether anything had been found with the more detailed sonar equipment being used today.
Once the wreckage was found, the navy would have to determine if it was at a "dive-able depth" before sending divers down, Harper said.
The wreckage could be at up to 60 metres deep, where specialist equipment would be needed because of decompression issues
A 400m wide exclusion zone is in place around the crash area, but a wider underwater search is being conducted.
BOUY DEPLOYED AS SEARCHERS' GUIDE
Waikato police Search and Rescue operation head Sergeant Warren Shaw earlier said: "At the time the debris was found, a buoy was deployed to guide searchers back to the site and to use as a starting point for locating the aircraft.
"Specialist police divers then travelled to the site yesterday and began mapping areas of the ocean floor around the buoy."
Shaw said police divers, working with mine countermeasures staff and navy divers would use unmanned equipment to search the sea floor.
"They bring with them a number of unmanned submersible devices that can assist in this and it is only when the aircraft has been pinpointed that we would consider putting any divers in the water.
"One of the major challenges we are facing is that we are dealing with an aircraft that has potentially impacted with the water at high speed and broken up."
He said it was also difficult to establish a starting point because of the potential for objects from the wreckage to drift up to 5km a day due to surface and sub-surface currents.
Spotters in helicopters were also conducting shoreline searches.
"We, of course, hope that we locate the aircraft and its occupants today, but even if it was the case, the wreckage would be at a depth near the edge of the operating capacity of the resources at hand and police are thus relying heavily on the expertise of the navy and their experience in this field."
Police say the debris field near Gannet Island suggested the Hertzs hit the water at high speed.
CIVIL AVIATION TO INVESTIGATE
The Civil Aviation Authority will investigate the cause of the crash, but Hamilton-based airline aviation expert Ewan Wilson, who spoke to Hertz just a day before the accident, said when a twin-engine plane lost an engine, it did not usually result in a fatal crash.
Wilson did not want to speculate on the cause of the crash, but other media have reported that Hertz had radioed Airways New Zealand to report engine failure and seconds later vanished off the radar screen.
"It would be unusual to ditch an aeroplane with only one engine down,'' Wilson said.
"And it would be unusual for an aeroplane like the Beechcraft Baron to crash with a single engine failure," he said.
Wilson met the Hertzs on Good Friday at Waihi Beach airport and they wished each other a happy flight.
But just after noon the next day, the couple's aircraft plummeted from the sky.
Wilson remembered them as a "happy couple" who were "really passionate about aviation". He had discussed aviation and aircraft at length with Hertz and was probably one of the last people to do so.
Conditions at the time of the accident were fine and clear and Hertz, who had 10 years' flying experience, was instrument-rated. One of his brothers is a United States Navy aviation instructor.
The crash is an eerie echo of a 2005 tragedy in which liquor magnate Michael Erceg and companion Guus Klatte were killed when their helicopter crashed into a forested area between Kawhia and Raglan.
HERTZ A KEEN AVIATOR
A keen aviator, Hertz had flown extensively in his homeland and in New Zealand.
Last year he won a gold medal at a vintage airshow in Wisconsin for a World War II-era Beech 17 plane he also owns.
Two Civil Aviation Authority investigators were preparing to study the cause of the crash yesterday.
The CAA could not start work until the crash scene was made available by police, who were taking all steps to find the occupants, spokesman Mike Richards said.
"The task of examining the wreckage will be quite difficult because of the depth of water."
Decompression sickness can be experienced at depths beyond around 30 metres, so the CAA would need specialist equipment and divers.
- Waikato Times