In a move that could complicate one of the U.S. Air Force’s most important and politically sensitive weapons programs, Northrop Grumman Corp. is threatening to shun a competition against Boeing Co. for aerial-refueling planes because of concerns over the bidding rules, the Wall Street Journal reports.

Northrop officials have hinted for months about quitting the race for the decades-long program, valued at $100 billion or more, if they don’t think the Los Angeles company has a fair shot of winning. Late last week, Northrop officially warned the Air Force in writing that it may not bid, according to people familiar with the matter. These people said Northrop officials believe draft bidding guidelines effectively favor Boeing’s less-expensive refueling plane because they don’t lay out detailed criteria for how the Air Force will evaluate extra capabilities, such as cargo and passenger capacity, that Northrop’s proposed airplane offers.

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