Simonson said the availability of "very powerful" AS350 B3 helicopters that can function in the thin air that high up the mountain was essential to saving more lives.
"They're quite remarkable," Simonson said. "Had this happened a year or two ago it would have been impossible to fly to the site of the avalanche."
"The helicopters were able to come in and evacuate the people directly from there, so they didn't have to find boots, clamp ons, climbing gear or things they would have needed to climb down," Simonson said. "So that was fortuitous."
A total of 231 climbers and guides were on the mountain but not all were at the higher camps hit by the avalanche.
The avalanche came at the start of Nepal's autumn climbing season, when the end of the monsoon rains makes weather in the high Himalayas unpredictable.
IMG's team is safely back at the base camp and is trying to decide if they should try the climb again or call it quits, Simonson said. This was the first time a team from IMG has climbed Manaslu.