Two Royal Air Force helicopters collided in mid-air in western England on Wednesday, killing one person and injuring three, two defense officials said. The Ministry of Defense said two Squirrel training helicopters from the RAF Shawbury base - home to the air force's helicopter training school - collided at the Tern Hill landing ground, 240 kilometers northwest of London. The ministry said four defense personnel were aboard the two aircraft. One was killed and one was seriously injured, while two had non life-threatening injuries, a spokesman said on the government's customary condition of anonymity. The names of the dead and injured personnel were not released pending notification of next of kin.