The U.S. Navy awarded a six-year, $805 million initial contract to build its MQ-25 Stingray aircraft to Boeing Co.

The program, which could ultimately be worth billions, was one that Poway-based General Atomics Aeronautical Systems Inc. had hoped to win.

The Navy announced its decision late Aug. 30.

The MQ-25 will be an unmanned, carrier-based refueling aircraft. Lockheed Martin Corp. was also in the running to build it.

Northrop Grumman Corp., which bases its unmanned programs in San Diego, walked away from the competition in November, saying it would not be worth its investment. Northrop Grumman built two prototype unmanned aircraft that successfully took off from and landed on a carrier deck.

About $12 million worth of subcontracting work on the Boeing project will be performed in San Diego, according to a Pentagon announcement. It was unclear which San Diego company would do the work.

The Navy sees the MQ-25 as an in-flight refueling aircraft that will extend the range of the manned fighters flying off the decks of aircraft carriers.

Under the deal, Boeing will design, build and support four MQ-25A unmanned air vehicles. The bulk of the work, some 46 percent, will be done in St. Louis. Work will continue through August 2024.

The Naval Air Systems Command of Patuxent River, Maryland awarded the deal.

Boeing, GA-ASI and Lockheed Martin had all done preliminary work on the MQ-25.

GA Aeronautical Systems already has a thriving business building its Predator family of remotely piloted aircraft for the U.S. Air Force, U.S. Army and overseas customers.

The Poway business is also at work on other projects. GA-ASI recently won a cooperative agreement with NASA to demonstrate unmanned aircraft flight in domestic air space.

The business is an affiliate of privately held General Atomics.