The Pentagon has grounded its fleet of F-35 fighter jets after discovering a cracked engine blade in one plane. The problem was discovered during what the Pentagon called a routine inspection at Edwards Air Force Base, California, of an F-35A, the Air Force version of the sleek new plane. The Navy and the Marine Corps are buying other versions of the F-35, which is intended to replace older fighters like the Air Force F-16 and the Navy F/A-18.

All versions of a total of 51 planes were grounded on Friday pending a more in-depth evaluation of the problem discovered at Edwards. None of the planes have been fielded for combat operations; all are undergoing testing.

The Pentagon said it is too early to know the full impact of the newly discovered problem.

A watchdog group, the Project on Government Oversight, said the grounding is not likely to mean a significant delay in the effort to field the stealthy aircraft.

Most expensive

The F-35 is the Pentagon’s most expensive weapons program at an estimated cost of nearly $400 billion. The Pentagon envisions buying more than 2,400 F-35s, but some members of Congress are balking at the price tag. — AP