The first phase of re-entering the Pike River mine has been completed, the New Zealand Defence Force says.
Work began last weekend removing material from the top of the West Coast mine in preparation for an attempt to re-enter it.
The Defence Force is providing assistance to Solid Energy, using a helicopter to hoist material from the top of the mine's ventilation shaft to clear the area for stage one of the project.
The work began nearly three years after 29 men died in the mine during a series of explosions.
The five-day operation saw a combined Defence Force team of Royal New Zealand Air Force personnel and 12 specialist NZ Army personnel deployed in support of the mission.
Using one of the RNZAF's new NH90 choppers, the team removed 18 loads involving 35 tonnes of debris from the mine's ventilation shaft.
Acting commanding officer of the Helicopter Transition Unit, Squadron Leader Anna Shaw, said aside from one day of rain, the complex operation went without a hitch.
"We were unable to fly operations on Tuesday because of the weather in the area, but this allowed our crews to break from their hard work and conduct a debrief of the operation with Solid Energy.
A NZ Army Movement Operator at the ventilation shaft rigging the loads, LCPL Zeke Lytollis, said the operation was an excellent test of skills.
"Some of the loads we were removing were far from conventional and at the upper end of our weight limits. When we're rigging the loads we have to look at the complete method of flight and make sure that what we put under the helicopter doesn't move or put too much stress on the key elements."
Some of the individual loads that were removed were up to three tonnes - twice the weight that civilian helicopters available to Solid Energy were able to remove.
Early last month Prime Minister John Key pledged $10 million of government support for a re-entry plan if it was safe, technically feasible and financially credible.
The staged 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.
While most of the bodies were believed to be inside the mine's main workings, the families believe some men may have been inside the drift when blasts ripped through the mine on November 19, 2010.
By the numbers:
* total Personnel: 33
* RNZAF Personnel: 21
* NZ Army Personnel: 12
* loads removed: 18
* weight of loads removed: 35 tonnes
* distance each load flown: 7km
* hours flown: 15 hours.