Craig Patterson, avalanche forecaster, killed. Why didn't his air bag save him?

Authorities Friday were investigating a fatal avalanche involving a backcountry professional who deployed a special air bag but didn't survive a snow slide in the Wasatch mountains east of Salt Lake City.

Craig Patterson of Park City was a veteran backcountry skier for the Utah Department of Transportation since 2006. He was scouting terrain Thursday for avalanche danger in Big Cottonwood Canyon.

Officials for UDOT and the Utah Avalanche Center were at a slope under 10,403-foot Kessler Peak on a divide between Big and Little Cottonwood canyons, home to four of Utah's resorts including Alta and Snowbird.

Patterson, 34, was among eight backcountry professionals for UDOT who climb mountains on skis and drop explosives to set off avalanches, usually early in the morning before ski resorts open. They also fire cannon shells from fixed positions, working round-the-clock shifts to keep slides from endangering motorists on canyon roads.

"It's a big responsibility," UDOT spokesman Adam Carrillo said Friday. "They don't take it lightly, and a lot of times they end up going out on their own because there's a lot of terrain to cover."

Patterson's body was recovered just before 1 a.m. Friday.

"He was able to deploy his air bag," Carrillo said. "He did everything he needed to do."

Air bags for skiers, often built into backpacks, are fairly new technology. They were first developed in Europe, where a Swiss avalanche institute says they have saved hundreds of lives. There were introduced in the Rocky Mountains a few years ago at prices from $600 to more than $1,000.

The air bags are designed to keep skiers afloat in an avalanche, but skiers can still be dragged over rocks or into trees. He also had an AvaLung, a device that allows someone to breathe if caught in snow.

UDOT has never lost an avalanche forecaster before, Carrillo said.

The agency is evaluating whether it should require the backcountry avalanche-control workers to work in pairs so one can dig the other out from any slide, he said.

"This is a one-of-a-kind incident," he said. "It's strategic loss to our family."

Avalanche work can be risky. In December, a veteran ski patroller was buried by a slide intentionally set by another member of his patrol at Alpine Meadows near Lake Tahoe.

Bill Foster, 53, died of injuries a day later.

Utah Gov. Gary Herbert said Patterson was a "dedicated state employee who was admired and respected for his professionalism and expertise in making our canyons safer for countless Utahns."

Patterson leaves a wife and six-year-old daughter and "will be dearly missed," the governor said.

By late Friday, there was still no report from investigators at Kessler Peak.

Copyright 2013 The Associated Press.