Seven weeks after the U.S. Air Force declared its first F-35 jets to be combat-ready, 10 of the aircraft aren't flying after service mechanics discovered "peeling and crumbling" insulation wrapped around lines that carry liquid to cool combat systems and computers.
The poor insulation is suspected on 57 aircraft, including 42 on Lockheed Martin Corp.'s production line. The issue is not a design flaw with the aircraft, called the Lightning II, but manufacturing glitches at one of two subcontractors that make the 18 lines through which the coolant flows, according to an Air Force statement and an interview with a service official, who asked not to be identified.
This includes six of the F-35A fighters that belong to Japan.