Beechcraft Corp. is protesting a light air support aircraft contract given to Embraer of Brazil and the Sierra Nevada Corp. by the U.S. Air Force.

Beechcraft said Friday its formal protest is being lodged with the U.S. Government Accountability Office.

"Following our debrief with the Air Force earlier this week, we are very perplexed by this decision," said Beechcraft Chief Executive Officer Bill Boisture. "Our belief that we have the best aircraft was confirmed by the Air Force rating our aircraft 'exceptional,' and the fact that we are the lower-cost solution was confirmed by the USAF's public award announcement."

Beechcraft produces the AT-6 light air attack aircraft, a single-engine turboprop that can also be used in training. Embraer produces the A-29 Super Tucano, which it offered for the Air Force's Light Air Support program.

Embraer won the contract -- for an initial 20 aircraft for Afghanistan's air force this month in a re-competition after Hawker Beechcraft filed a complaint and SNC filed a federal lawsuit.

A subsequent Air Force investigation found "evidence of bias" toward Embraer and SNC, which led to the re-competition.

Hawker Beechcraft recently emerged from Chapter 11 Bankruptcy as Beechcraft Corp.

"We simply don't understand how the Air Force can justify spending over 40 percent more -- over $125 million more -- for what we consider to be less capable aircraft," Boisture said. "Given our experience of last year and our continued strong concern that there are again significant errors in the process and evaluation in this competition, we are left with no recourse other than to file a protest with the GAO.

"The Air Force needs to make the right decision for the nation and our future allies."

In a related development, a U.S. union representing aerospace workers on Friday joined in the controversy. The International Association of Machinists and Aerospace Workers said awarding the contract to a Brazilian aircraft manufacturer threatens 1,400 U.S. jobs and it called on the Air Force to reverse the contract award.

"We should be very concerned whenever U.S. taxpayer dollars are used to create hundreds of jobs in any foreign country," said IAM President Tom Buffenbarger. "We should be outraged when the loss of those jobs also threatens vital U.S. economic and national security interest.

"I don't know why the U.S. government is bending over backward to accommodate Brazil in the midst of sequestration but this is a real blow to American workers and taxpayers. The claim by Embraer that most of their plane would be 'built in the USA' adds insult to the injury of the 1,400 jobs that will be destroyed here at home."

The IAM says it represents more than 3,000 active and laid off Beechcraft workers.