Officials say everything possible is being done to find a New Zealander and two Australians on board a helicopter that went down in dense jungle in Papua New Guinea.
Thick forrest and fog have hampered the search since the Bell 206 went down on Friday afternoon outside Mt Hagen in the PNG Southern Highlands.
Two of the missing men have been named tonight by the helicopter operator, Hevilift.
They are Australian pilot, Captain Russell Aitken, 42, and 49-year-old New Zealander and deputy chief pilot, Captain Antony Annan.
A 37-year-old Australian pilot has not been named at the request of the family, the company says.
"We ask that media respect the fact that the families are deeply concerned about the whereabouts of their loved ones and request that they are left alone at this difficult time," said Hevilift group managing director Paul Booij in a statement.
"A second full day of searching has been completed without any sightings of the helicopter or of Hevilift's missing crew."
Booij said search crews were employing a methodical approach to the rescue.
"Aerial search needs to be methodical, this is a standard approach used globally. We have, therefore, been following a grid search pattern to ensure that we do not miss an area within the search envelope."
Australia's high commissioner to PNG, Ian Kemish, said he is satisfied everything possible is being done to find the men.
Returning from a trip to Mt Hagen today, Kemish said Hevilift is conducting the search using local pilots, as well as being aided by a ground search team from a nearby InterOil drilling station.
"For the moment we think the most effective search is the search being conducted by people with local knowledge," he said.
"We want to be as effective as possible and that's by using local knowledge and resources.
"The area is almost unpopulated. There's the occasional village and significant areas are not accessible even on foot. It is rough topography.
Kemish said Australian search and rescue co-ordinators were drawing up search grids to be used by the seven helicopter pilots sweeping the area.
"Seven is pretty much (all) the airspace and local infrastructure can support," he said.
The Australian and PNG defence forces, Australian search-and-rescue teams, ExxonMobil PNG workers and Hevilift clients were assisting in the search.
Australia currently has military aircraft and military advisers in PNG as part of the joint Australia-New Zealand Task Force to assist with the national elections.
Hevilift group managing director Colin Seymour says the search was widened on Sunday, with several hoist-equipped choppers on standby for when the plane and crew are found.
The efforts also now involve a search-and-rescue officer attached to the task force, which the Australian High Commission says is maintaining close contact with the PNG Search and Rescue Coordination Centre.
"The search is being run out of Mt Hagen and I understand the search patterns are changing to suit the weather," Seymour said.
The helicopter was reportedly flying in low cloud with reduced visibility and Hevilift said a mayday call was broadcast about five minutes after the chopper left a drill rig site at 3.25pm (local time) on Friday.
It's believed those on board were on their way to refuel before returning to their Mt Hagen base.