Sixteen unusable transport aircraft that the U.S. government bought for the Afghan Air Force have been scrapped for pennies on the dollar, according to the Special Inspector General for Afghanistan Reconstruction.

All told, the Defense Department spent $486 million for 20 G222 planes, of which 16 were sold as scrap to an Afghan construction company for about $32,000, the office announced Thursday in a news release. The remaining four planes are being stored at Ramstein Air Base, Germany.

The Air Force let the contract for the planes — designated as C-27As by the U.S. government — with Alenia Aermacchi North America expire in March 2013 because the planes were often grounded due to a lack of spare parts.

After flight operations ended, the 16 planes in Afghanistan sat on the tarmac at Kabul International Airport until they were recently scrapped by the Defense Logistics Agency and sold for 6 cents per pound of scrapped material, wrote John F. Sopko, Special Inspector General for Afghan Reconstruction, in an Oct. 3 letter to Air Force Secretary Deborah Lee James.

"I am concerned that officials responsible for planning and executing the scrapping the planes may not have considered other possible alternatives in order to salvage taxpayer dollars," Sopko wrote.

Sopko has requested from the Air Force all documentation related to the decision to scrap the planes, including whether any alternatives were considered and what will happen to the four remaining planes. He also wants to know if the Air Force has taken any action against the companies responsible for building and maintaining the planes and if the service made any efforts to return the planes for a refund.

The 16 G222 aircraft were scrapped "to minimize impact on drawdown of U.S. forces in Afghanistan," a Defense Department spokesman said.

"The Department of Defense and U.S. Air Force will consider plans for the remaining four aircraft and associated items located in Germany consistent with existing disposition procedures, to include screening for outside interest," the spokesman said in an email. "The Department of Defense (DoD) strives to ensure every reconstruction project is executed in a manner that demonstrates responsible stewardship of taxpayers' dollars."

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In December 2012, Sopko wrote a letter to Defense Secretary Chuck Hagel as well as the commanders of U.S. Central Command and U.S. troops in Afghanistan announcing that his office had begun a review of the G222 program.

"Despite spending at least $486.1 million in acquisition and sustainment costs on the program, DODIG [Defense Department Inspector General's office] reported the aircraft flew only 234 of 4,500 required hours from January through September 2012," Sopko wrote in the Dec. 5 letter. "The DODIG also concluded that an additional $200 million in Afghan Security Forces Funds might have been spent on spare parts for the aircraft to meet operational requirements, noting that several critical spare parts for the aircraft were unavailable."