Boeing Company (NYSE:BA) shares slipped Thursday after fresh uncertainty emerged around one of its most closely watched commercial deals, even as the aerospace giant secured another U.S. military contract.On Wednesday, the U.S. Air Force awarded Boeing a contract exceeding $173 million to supply eight additional MH-139A Grey Wolf helicopters, along with training and sustainment services.The aircraft, built to guard intercontinental ballistic missile fields, offer higher speed, range, and payload capacity to ...