The missing Malaysia Airlines plane's abrupt U-turn back toward Kuala Lumpur was programmed into the plane's on-board computer long before the co-pilot gave his customary-sounding sign-off to Malaysian air traffic control, sources tell NBC News. The change in the plane's direction was made at least 12 minutes before the "all right, goodnight" to controllers on the ground, according to the sources. That suggests the plane's puzzling turn back was planned and executed in the cockpit before the plane disappeared from radar — but it doesn't necessarily indicate an ulterior motive. "Some pilots program an alternate flight plan in the event of an emergency," a former NTSB investigator told NBC News. The development comes after authorities said Saturday for the first time that the jet veered from its flight plan because of a "deliberate action" by somebody on board.