The U.S. Air Force awarded a contract to Northrop Grumman Corp. on Tuesday to build its next generation stealth bomber for a price tag of $60 billion. At least some of the construction for the Long-Range Strike Bomber program will take place at Northrop’s manufacturing facility at Plant 42 in Palmdale. The military expects to need 80 to 100 planes. The new bomber will replace the B-52 Stratofortress and the B1-B Lancer, commissioned during the 1980s and built by Boeing. The B-2 Spirit stealth bomber made by Northrop in Palmdale will remain in service. “The Long-Range Strike Bomber will be the backbone of the Air Force’s future strike and deterrence capabilities,” Secretary of Defense Ash Carter said in announcing the contract. Northrop, in Falls Church, Va., beat out a competing bid from Boeing Co., in Chicago.