U.S. intelligence analysts conclude the Russian plane was not brought down by surface-to-air missile. An American infraredsatellite detected a heat flash at the same time and same place over the Sinai as the plane, but no evidence a missile was involved. Analysts believe it could have been some kind of explosion on the aircraft itself, either a fuel tank or a bomb. U.S. officials do not rule out that ISIL could have been responsible for bringing down the flight.