A firefighting supertanker jumbo jet has been grounded at its Victorville hub while fire officials investigate what caused the plane to make an emergency landing Monday night. The DC-10 airtanker used by the state firefighting agency, Cal Fire, was forced to return to Victorville about 5:20 p.m. Monday after it struck the top of several trees while fighting the White forest fire in Kern County, according to a statement by Cal Fire. The plane, which carries 12,000 gallons of water or fire retardant, struck severe turbulence near Bison Peak south of Tehachapi, but was able to apply power and...