Northrop Grumman Corp. has received multi-year contracts from the U.S. Air Force and U.S. Navy totaling nearly $12 billion.

The Defense Department late Wednesday said that the potential value of the Los Angeles defense contractor’s three-year contract to support the Air Force’s B-2 stealth bombers was increased more than 50 percent to $9.5 billion. There are 20 B2s in the fleet.

Separately, Northrop said it received a Navy contract valued at up to $2.4 billion to refuel and overhaul the nuclear-powered aircraft carrier Theodore Roosevelt. The job is expected to take three years and involve 3,800 employees at Northrop Grumman Shipbuilding division in Newport News, Va. The process will extend the life of the Nimitz-class supercarrier for 25 years, the company said.

“During this large and complex project, we’ll touch almost every part of the ship,” said Jim Hughes, Northrop Grumman Shipbuilding’s vice president of aircraft carrier overhaul and fleet support, in a statement.

Northrop shares were up 66 cents, or 1.4 percent, to $49.13 in midday trading on the New York Stock Exchange.