Two unrelated small-aircraft accidents occurred in the United States on Friday, according to local and federal officials. At about 8:49 a.m. local time, a single-engine biplane nosedived into a field just off a runway at Centennial Airport south of Denver. South Metro Fire Rescue said the lone person aboard escaped injury. Crews contained a minor fuel leak and worked to right the aircraft; damage appeared limited to one wing. Airport officials are expected to release additional details. Roughly five hours later, a Cessna 185 went down near Bangor International Airport in Maine at around 1:45 p.m. The pilot, the only occupant, was pronounced dead. Bangor police, fire units and the Air National Guard responded, and the airport closed its runway while the site was secured. The Federal Aviation Administration and the National Transportation Safety Board have opened separate investigations into the causes of both crashes.