After Malaysia Airlines Flight 370 veered off its course, civilian air-traffic controllers spent precious predawn hours in befuddled exchanges with counterparts in nearby countries in an effort to locate the jet, according to documents released by investigators Thursday. A series of missteps began less than an hour after the plane disappeared around 1:20 a.m. on March 8.... Through that first stretch, the carrier's operation center continued to advise controllers that the plane was in "normal condition," remained in contact with ground facilities and was flying somewhere in Cambodian airspace—an area that was never on its flight path from Kuala Lumpur...