Two Australian men in their early 20s had to be rescued by helicopter near the Bonar Glacier while attempting to climb Mount Aspiring on Tuesday evening (December 2).

Wakatipu Alpine Cliff Rescue Team coordinator Russ Tilsley said the pair set off their personal locator beacon at 8pm after realising they couldn’t go on due to severe exhaustion.

The Otago Southland Rescue Helicopter was dispatched with two Wakatipu Alpine Cliff Rescue volunteers on board. It was able to land near the pair and pick them up.

“They’d got up just across the Bonar Glacier and were completely and utterly exhausted,” Russ said.

“One of them had collapsed he was so exhausted, so they had to raise the alarm.

“It’s a long hard climb and they’d underestimated what was involved.”

Russ said the men were 'walking in' on the first day of a planned two-day climb.

“It’s a long way in and they’d underestimated the distance and obviously weren’t fit enough and in condition,” he said.

The Otago Southland Rescue Helicopter dropped the pair to their car at Raspberry Flat.