Top Pentagon officials are not happy with the progress of development and testing of the F-35 joint strike fighter, Reuters news service reported.
Citing unnamed sources, Reuters described as "very painful" a four-hour meeting Friday of a defense acquisition board.
No decisions were reached as a result of the meeting, which a Pentagon spokeswoman said was held to review the status of the development.
But the report indicates serious concern expressed at the meeting about software development and testing, the high-tech helmet that will give the pilot cues from all the sensors about targets and aircraft performance, and other performance issues.
Asked for comment Tuesday, Lockheed Martin issued a statement by Steve O'Bryan, one of its top F-35 program executives.
"The technological challenges facing the program are being addressed and the program is making good progress," O'Bryan said. "These kinds of challenges are normal in a developmental program."
Lockheed is developing the F-35 in its west Fort Worth facility, where it assembles the aircraft and prepares them for delivery to the armed forces.
The review comes as Frank Kendall, the Pentagon's chief weapons buyer, and other high-ranking officials move toward 2014 budget decisions.
In each of the last three years the Pentagon has cut back planned F-35 production and shifted funds to speed development and testing, with emphasis on software writing and testing.
Lockheed, the Pentagon's F-35 joint program office and the military services have issued a steady stream of news releases in recent months highlighting progress in flight testing.
Last week the Air Force said it will start a 65-day review of the F-35's readiness for pilot training at Eglin Air Force Base in Florida.