By Andrea Shalal-Esa

WASHINGTON (Reuters) - Senior Pentagon officials voiced frustration about the pace of Lockheed Martin Corp's development of the $396 billion F-35 Joint Strike Fighter program at a high-level review on Friday, according to several sources familiar with the program.

Officials did not approve a comprehensive plan for operational testing of the F-35 program as had been expected.

The Pentagon's Defense Acquisition Board huddled for more than four hours on Friday evening in a meeting described by one participant as "very painful" given ongoing challenges facing the high-tech F-35 helmet that is integral to the craft's weapons systems.

Marine Corps Commandant General James Amos told Reuters in an interview on Saturday that he had not been briefed on Friday's review meeting, but said he was closely following work on the helmet, since its completion was needed to allow operational use of the new jets.

"The helmet is a critical piece that needs to be solved," Amos said, noting that the Marines urgently needed the short takeoff, vertical landing (STOVL) version of the plane to replace their aging fighter jets, which include older model F/A-18 Hornets built by Boeing Co..

The Marine Corps had hoped to become the first military service to start using the new F-35B jets this year, but a series of program restructurings has pushed that date back several years.

If the helmet being developed by Vision Systems International (VSI), a joint venture between Israel's Elbit Imaging and Rockwell Collins succeeds, it will be the most advanced ever built.

It is supposed to let pilots see data from all the plane's sensors, effectively allowing the pilot to look right through the floor of the plane and all around it. But the project has run into problems with night vision, delays in displaying the data and a green glow at the visor's edges.

Lockheed Martin has brought in an alternate contractor, BAE Systems to work on a substitute helmet in case the VSI helmet does not meet its deadlines. Current F-35 program manager Navy Admiral David Venlet is meeting with BAE officials during a trip to Europe this week.

Lockheed has also agreed to provide an F-35 jet for dedicated testing of the helmet in coming weeks, the sources said. "These kinds of challenges are normal in a developmental program," Steve O'Bryan, a Lockheed executive, said.

Lockheed officials, who were not at the meeting, said on Monday, technological challenges facing the program were being addressed.

It is not just helmet problems that are afflicting the fighter jet. There are also the high costs of maintaining and operating the aircraft as well as flaws in its software code.

And there are problems as well with Lockheed's internal system designed to track the cost of the F-35 program, said the sources, who were not authorized to speak publicly.

FLIGHT TESTING

The sources said F-35 flight testing was going well, and initial training flights were taking place at Eglin Air Force Base, but Pentagon officials are increasingly frustrated that the technology issues were taking so long to resolve.

"More progress is needed on the complex development activity," said one of the sources. "There's frustration that it's not happening fast enough."

Lockheed, the Pentagon's No. 1 contractor, is developing and building three variants of the new F-35 fighter for the U.S. Air Force, Navy and Marine Corps and eight foreign countries that are helping to fund its development -- Britain, Australia, Canada, Norway, Denmark, Italy, the Netherlands and Turkey.

Lockheed officials say the program is making progress, but lawmakers, like the Pentagon, are unconvinced.

The Pentagon's director of testing and evaluation has also repeatedly underscored the need for more testing before the Air Force and Marines start training pilots.

Pentagon spokeswoman Cheryl Irwin declined comment on the closed-door meeting, except to say that it was aimed at providing a status update and no major decisions were made.

The Pentagon's F-35 program office also declined comment, but said officials were keeping a close watch on the program.

"All the technical issues are known and engineering solutions are either in work or being developed to deliver the F-35 to the warfighter," said Joe DellaVedova, program spokesman.

The Marine Corp's Amos said the F-35 program was making progress, and he did not expect huge new problems like the bulkhead cracks that had cropped up in recent years.

The Pentagon's Defense Contracts Management Agency also gave an update on its work monitoring Lockheed's Earned Value Management System after announcing in June that it would withhold 5 percent of the price of the fifth lot of production planes due to continued shortcomings with the system.

"We're not happy that they're not certified. However, the data they provide is still useful for monitoring performance on the program," DellaVedova said.

Major General Christopher Bodgan, who will take over as program manager for the F-35 program at the end of the year, was slated to speak about the program at an Air Force Association conference on Monday.

It will be his first major public appearance since moving to the F-35 program from his previous job managing the Air Force's new refueling tanker.

(Reporting By Andrea Shalal-Esa; Editing by Leslie Gevirtz)