The chief executive of New Zealand mobile phone company 2degrees and his wife were onboard the light aircraft that plunged into the sea near New Zealand North Island region of Waikato on Saturday.Eric and Kathy Hertz have been missing since the twin-engined aircraft disappeared off the radar at 12:20 p.m. near Raglan, Radio New Zealand reported.Rescuers called off a search for the pair on Saturday evening but will resume at first light on Sunday.Eric and Kathy Hertz were travelling from Ardmore to Timaru when the plane\'s engine failed and lost contact with Airways New Zealand.Oil and the wreckage was located 20 km from the entrance to Kawhia Harbour, near Waikato on the west coast of the North Island.A statement on 2degrees\' website said the pair are unlikely to have survived.Rescue Coordination Centre spokesperson Steve Rendle said they would have been found by now, if they had survived the crash. He said where the plane went down has been searched without success by a helicopter, an aircraft and a coastguard vessel.\"(We have) intensively searched that area. Unfortunately there has been no sign of the two people that had been on board, so we\' ve handed the matter to the police,\" he added. Endi