F-35 forced to land in Texas. Why?

One of two F-35 fighter jets headed to a Nevada air base made an unscheduled landing in Lubbock, Texas on Monday after a caution light came on in the cockpit, according to a Pentagon spokesman and the plane's manufacturer, Lockheed Martin Corp.

The F-35, a next-generation stealth fighter, was flying from the Lockheed plant in Fort Worth, Texas to Nellis Air Force Base near Las Vegas on Monday afternoon, when a caution warning light came on, requiring the pilot to land at the nearest airport, said Lockheed spokesman Michael Rein.

He said the pilot landed safely. The second F-35 aircraft landed as planned at the Nevada air base, joining two other F-35 aircraft that arrived there last week, where they will be used for operational testing and evaluation of the new warplane.

A team of Lockheed maintenance experts was en route to examine the single-engine plane at the Lubbock airport, which is about 300 miles from Fort Worth, Rein said. It was not yet clear what caused the caution light to come on, he said.

The incident is the latest in a string of negative news about the new single-seat, single-engine warplane that Lockheed is developing for the U.S. Air Force, Navy and Marine Corps, and eight international partners: Britain, Canada, Australia, Italy, Turkey, Norway, Denmark, and the Netherlands.

The F-35 Joint Strike Fighter, the Pentagon's most expensive weapons program, has been grounded twice this year already for engine-related issues.

Joe DellaVedova, spokesman for the Pentagon's $396 billion F-35 program, confirmed the plane had landed in Lubbock after a warning light came on, but said he had no further details about the incident.

Rein said it was not immediately known if the warning light was triggered by a problem with the engine, which is built by Pratt & Whitney, a unit of United Technologies Corp.

He said local police were securing the state-of-the-art warplane at Lubbock Preston Smith International Airport, which handles operations by three airlines and several cargo carriers.

Rein said the plane would continue its journey to Nellis Air Force Base, or return to the Lockheed plant, depending on what the mechanics discovered when they examined the plane.

Gary Loftus, airport operations manager at the Lubbock airport, told Reuters the F-35 fighter was parked on an airport ramp and was protected within a fence. "Nobody can get to the airplane," he said.

He said he believed it was the first time an F-35 fighter had landed at the commercial airport.

The congressional Government Accountability Office on Monday released its annual report on the weapons program, saying it was showing progress in development, production and technical issues but still faced tremendous challenges.

On Feb. 28, the Pentagon cleared the aircraft to  resume flights following a week-long precautionary grounding imposed after a crack was found on an engine blade on a test plane in California.

"F-35 flight operations have been cleared to resume," Pentagon spokeswoman Kyra Hawn said in a statement. No additional cracks were found during inspections of engines on the remaining 50 planes in the Pentagon's fleet, or any spare engines, Hawn said.