He told the company's annual general meeting that the company was also keen on maintaining high performances from the mine in this financial year.
"Narrabri Stage 3 is a significant life extension and optimisation that necessitates a re-approval of the site," he said.
"The central focus is the incorporation of the southern Exploration Licence and the approval of extraction of the coal in extended longwall panels up to 10 kilometre in length.
"This expansion will see the life of project be extended to 2044."
The company has submitted the Environmental Impact Study for the project to the NSW Department of Planning, Industry and Environment for adequacy review. The EIS went on public display late last week.
There was a significant uplift Narrabri's run-of-mine production for the second half of FY20 as the longwall returned to running at normal capacity, with a record 1 million tonne month in April.
"Not many underground mines in Australia can claim that," Flynn said.
"Looking forward to FY21, we are guiding ROM production of 6-6.7Mt. Guidance reflects a longwall move from LW109 to LW110 in Q3 FY21.
"This guidance level is consistent with operating at depth until we move back to shallower ground in the southern panels where historical levels of volumes and costs are much improved."