Lockheed Martin and Sikorsky have filed protests with the U.S. Government Accountability Office against the Air Force award of its combat, search and rescue (CSAR-X) helicopter program to Boeing Co., an acquisition deal worth between $10 billion and $15 billion.

Sikorsky filed its appeal Nov. 17. A company release said, "Sikorsky seeks to ensure the selection process accurately evaluated the characteristics and performance of its HH-92 helicopter."

Lockheed filed its appeal Nov. 20. The company rarely files such protests, said company spokesman Greg Caires.

"We are taking this step with reluctance because we appreciate that our nation's warfighters need a new CSAR helicopter," Caires said. "However, it is precisely because of our understanding of this vital mission, and our continuing belief that Team US101 offered the most capable and most affordable solution, that we have requested the GAO's review. This review will give us the opportunity to more fully understand the reasons for the decision that was made."

Air Force officials declined to comment.

Lockheed believes the criteria the Air Force used for the competing proposals were not applied uniformly, Caires said. "The competitors received different instructions during the competition."

This prevented a fair and equitable evaluation, according to Caires.

Boeing put the program's value at about $10 billion, while the Air Force has said the cost could be up to $15 billion. There's no discrepancy, Boeing said, because the Air Force cost estimates include operations and maintenance estimates which the company does not.

Protests aside, industry experts and analysts continue to wrestle to find a broader meaning behind the Air Force decision.