New Delhi, Aug. 2 -- SAN DIEGO - The ejection seat did its job. The $135.8 million aircraft did not.

A Marine Corps F-35B Lightning II fighter broke into two pieces Friday morning after an emergency ejection on the flight line at Marine Corps Air Station Miramar, igniting a brush fire that spread across a football-field-sized section of terrain north of State Route 52 and drew firefighting crews from the San Diego Fire-Rescue Department. The pilot was transported to a local medical facility in stable condition with non-life-threatening injuries.

The Marine Corps classified the accident as a Class A mishap, the most severe category in the military's incident hierarchy, reserved for events involving a fatality, permanent disability, or th...