Boeing Co (BA.N) may decide as soon as Thursday whether to protest the U.S. Air Force’s selection of Northrop Grumman Corp (NOC.N) to develop and build a next-generation long-range strike bomber amid signs that a challenge could be an uphill battle, according to sources familiar with the issue. Boeing spokesman Todd Blecher said the company had not yet decided whether to challenge the contract award, which could be worth $80 billion to the winning bidder over the next decades.