By DENISE LAVOIE and BEN FINLEY
RICHMOND, Va. (AP) — An aviation expert is citing a loss of oxygen as a possible theory for why an unresponsive business jet flew over the nation’s capital Sunday before crashing in rural Virginia. Investigators are just beginning to look for answers. The Cessna Citation took off from Elizabethton, Tennessee, headed for Long Island’s MacArthur Airport. Once over Long Island, it turned around and flew a straight path over Washington, D.C. before crashing in a mountainous part of Virginia. Federal investigators said Monday the pilot and three passengers were killed.