The Air Force's C-17 cargo aircraft continue to show off their versatility, most recently in an airdrop of 22,372 pounds of supplies to the South Pole on Tuesday.

Twenty containers were delivered in two passes for the National Science Foundation and U.S. Antarctica Program during the mission, led by the 13th Air Force, which has its headquarters at Hickam Air Force Base.

The airdrop was the second time the C-17s have demonstrated their abilities at the South Pole. Their first Operation Deep Freeze mission was on Dec. 19, 2006.

"This mission is testimony to the flexibility and reach of air power," said Lt. Gen. Chip Utterback, commander of the 13th Air Force. "The airlift, sealift and ground support capability executed by an integrated total force team operating in an unforgiving and unique environment make Operation Deep Freeze a one-of-a-kind mission."

The supply operation involves active-duty and reserve C-17s from McChord Air Force Base in Washington state; New York Air National Guard LC-130 aircraft equipped with big skis; Coast Guard and commercial ice breakers; and U.S. Navy port services at McMurdo Station.

The use of the C-17 versus the LC-130, which lands on the ice, allows four times the delivery on a single airdrop.

The Hawai'i Air National Guard and active-duty Air Force jointly operate their own C-17 aircraft at Hickam, and missions have taken the aircraft throughout the Pacific and into Iraq and Afghanistan.

C-17s can land on dirt runways and many airstrips that can't take the weight of the larger C-5 Galaxy.

Operation Deep Freeze is one of the most demanding peacetime operations because of the harsh environment at the South Pole.

During the winter, temperatures often dip as low as 100 degrees below zero, which can paralyze an aircraft's hydraulic system, crystallize fuel and solidify lubricants, the Air Force said.

Airdrops take place at about 10,700 feet above sea level, with crews wearing oxygen masks. The South Pole is about 9,300 feet above sea level.

The Air Force has supported the National Science Foundation and U.S. Antarctica Program since 1955.

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