The airline Monday ruled out pilot error or a technical fault, but Russian aviation officials dismissed those comments as premature.

CBS News' national security correspondent David Martin reports a U.S. infrared satellite detected a heat flash over the Sinai at the time the Russian plane went down. The data is still being analyzed in an effort to determine what caused the flash. One possibility is a bomb, but an explosion in a fuel tank or engine as the result of a mechanical failure is also possible.

Some aviation experts raised the possibility that a bomb on board the Metrojet Airbus A321-200 brought it down, while others cited an incident in 2001 when the aircraft grazed the runway with its tail while landing.