By Andrea Shalal RAF FAIRFORD England (Reuters) - The U.S. Navy on Friday maintained a grounding order for F-35 B-model and C-model fighter jets built by Lockheed Martin Corp, saying it was still not clear what caused a massive engine failure on an Air Force F-35 jet on June 23. "At this time, I do not have sufficient information to return the F-35B and F-35C fleet to flight," Vice Admiral David Dunaway, who heads the Navy's Air Systems Command, said in an update to a fleetwide grounding order issued by U.S. officials on July 3. Dunaway said in the document that he was committed to returning the F-35 fleet to flight as soon as possible, but there was "no discernible event that represents a root cause." In the incident last month, the Pratt & Whitney engine on an Air Force F-35 A-model jet broke apart and caught fire while a pilot was preparing to take off from Eglin Air Force Base in Florida air base. Until the grounding is lifted, the U.S. Marine Corps and Britain will not be able to ferry four F-35B aircraft to Britain for the fighter jet's planned international debut at two air shows there this month - the Royal International Air Tattoo, world's largest military air show that began Friday, and the Farnborough air show, which starts on Monday and runs through July 20.
Seismologists said an earthquake that struck near Japan's shuttered Fukushima nuclear site early Saturday was an aftershock of the tremor that sparked 2011's deadly tsunami, and warned of more to come. The strong 6.8-magnitude earthquake off the Pacific coast of northeastern Japan caused a minor tsunami in the early hours, though authorities lifted all weather warnings roughly two hours later. Seismologist Yasuhiro Yoshida of the Japan Meteorological Agency said it was a delayed tectonic reaction to the 9.0-magnitude quake which left the Fukushima nuclear power plant in a meltdown crisis after the coast was ravaged by monster tidal waves in March 2011. "There are fears that relatively large earthquakes will occasionally occur in the ocean area where aftershocks of the great earthquake continue," he said.