Citing the apparent absence of a fire before impact in the latest crash, the Air Force said it does not plan to ground the nation’s B-1B bombers. The latest crash involving one of the $280-million jets was at Ellsworth Air Force Base in South Dakota last week. The Strategic Air Command “has not suspended flying of the B-1B or taken additional measures from what we did after” the crash Nov. 8 of another B-1B near Dyess Air Force Base in Texas, a spokesman said. Four crew members involved in the Texas crash ejected safely, as did the crew in the South Dakota crash. The planes, designed for nuclear bombs, carried no weapons.