Work to recover the 29 miners whose bodies are entombed in the Pike River coalmine begins this weekend.
Solid Energy and the Government - which has pledged $10 million towards body recovery - have approved a plan to re-enter the tunnel.
While most of the bodies are believed to be inside the mine's main workings, the families think that some men may have been inside the drift when blasts ripped through the mine on November 19, 2010.
The re-entry plan is designed to seal off the ventilation shaft in the mine's main entry tunnel, known as the drift.
The mine will be pumped full of nitrogen to force out any methane gas and allow experts to walk down a 2.3km shaft to a rockfall.
Preparatory work for the first stage of the re-entry is planned to begin this weekend, subject to weather, Solid Energy confirmed this morning.
Personnel and equipment from the New Zealand Defence Force will secure and lift material from around the top of the mine ventilation shaft - structures such as fan ducting and generator sets - to clear the area for stage one of the project.
The Defence Force will provide one Air Force NH90 helicopter, aircrew and maintenance personnel supported by a specialist team of NZ Army personnel for airlift operations.
A specialist rigging team of Army personnel will be based at each end of the airlift operation to load and unload the under-slung cargo.
Air Component Commander Mike Yardley says the Defence Force has the capability to respond at short notice for these types of operations and this is the first time an NH90 has been operationally tasked to support another government agency.
"The NH90 has twice the lifting capacity of civilian helicopters available to Solid Energy and therefore we are pleased to be able to provide assistance for this important task," Air Commodore Yardley said.
Today, Kath Monk, whose 23-year-old son Michael died in the blast, welcomed the start of re-entry work.
"All we've ever wanted is to give it one honest attempt at getting down the drift," she said.
"If that step is successful, then we go from there.
"It's all very positive, but we know we have to take it one step at a time, and reassess where we're at."
Solid Energy chairman Mark Ford says the start of re-entry work is significant for the Pike River family members who have been waiting for a long time.
"We are pleased to have reached this start point and to have the support of the New Zealand Defence Force in clearing the site," Mr Ford says.
"While Solid Energy is managing the project, it is very much a collaborative effort, with funding from the Government and the expertise of many experts and organisations have been brought together to plan it and safely carry it out."
It is expected the Defence Force's involvement will be completed by the middle of next week.