UPDATE 1-U.S. Marine version of Lockheed fighter takes off

(adds quotes from Pentagon, details on design, byline)

By Andrea Shalal-Esa

WASHINGTON, June 11 (Reuters) - The U.S. Marine Corps variant of Lockheed Martin Corp's (LMT.N) F-35 fighter jet, estimated to cost almost $70 million, completed its first conventional flight that lasted 44 minutes on Wednesday.

The F-35 aircraft, designated BF-1, took off at 10:17 a.m. CDT (1517 GMT), Lockheed spokesman John Smith said.

The Pentagon estimates the overall F-35 program, including research and development, will cost $298.8 billion. Each plane is forecast to cost almost $70 million, based on plans for the U.S. military to buy 2,443 F-35 fighter jets through 2034.

Lockheed and its partners, Britain's BAE Systems Plc (BAES.L) and Northrop Grumman Corp (NOC.N) are developing three variations of the F-35 or Joint Strike Fighter for the Air Force, Marine Corps and Navy. The plane is designed to perform close air support, tactical bombing and air superiority fighter missions.

The consortium, which also includes Pratt & Whitney, a unit of United Technologies Corp (UTX.N), General Electric (GE.N) and Britain's Rolls-Royce (RR.L), hopes to sell the fighters to other countries as well.

"This aircraft is going to only further enhance what is a tremendous asymmetric advantage ... in terms of controlling the air, taking advantage of intelligence, surveillance and reconnaissance capabilities, multi-sensor capabilities, and the ability, if need be, to drop a bomb in a precision strike," said Marine Corps Commandant Gen. James Conway.

The single-seat, single-engine fighter, designed to be based nearer front lines, is expected to be in the field in 2012. Graham Tomlinson, a former British military pilot, was the controls of the jet, guiding up to an altitude of 15,000 feet where he tested the F-35B's handling, engine-power variations and subsystems.

A Pratt & Whitney prototype engine powered the F-35B. The company had several engine blades snap off during earlier ground tests of the short takeoff/vertical landing (STOVL) mode.

The problem never affected the engine during conventional flight mode, the company said, adding it was on track to begin testing of the engine in STOVL mode later this year.

"We are working closely with our customers, Lockheed Martin and the joint program office; we have identified the root cause, and we are working toward a STOVL mode flight later this year," Pratt & Whitney spokeswoman Stephanie Duvall said.

The F-35 program is the world's largest military project, involving 11 countries, according to Lockheed. It employs about 20,000 people worldwide. (Reporting by Andrea Shalal-Esa; editing by Jeffrey Benkoe, Leslie Gevirtz)