WASHINGTON (Reuters) - The Pentagon and U.S. Navy on Friday ordered a temporary grounding of the Marine Corps version of Lockheed Martin Corp's F-35 fighter jet after an incident that occurred during a training flight at Eglin Air Force Base in Florida on Wednesday. The Pentagon's F-35 program office said the grounding affected all 25 F-35B model jets, while flights of the Air Force's A-model and the Navy's C-model were unaffected. Ground operations of the B-model planes continued. ...