Northrop Grumman said recently it may pull out of the competition to win a $40 billion contract to build a new Air Force refueling tanker. In a letter to several Pentagon officials, the defense firm argued the bidding process was stacked against it and said that without changes to the selection criteria, it could not submit an offer. Northrop’s withdrawal would leave Boeing as the only company bidding for the contract, which goes against congressional preferences for competition on all major defense contracts.Read more from Market Watch.