There are three leading theories regarding the loss of Metrojet 9268 on Oct. 31, 2015: 1) a missile fired from the ground, 2) mechanical malfunction which resulted in catastrophic damage, and 3) an explosion from inside the aircraft.

To recap the tragic flight, Metrojet 9268 took off from Sharm el-Sheikh International Airport headed for St. Petersburg at 5:51am local time (03:51UTC). At 6:14am, 23 minutes later, the aircraft disappeared from radar screens.

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An analysis of the flight parameters shows that at 04:12:58 UTC, just after passing 31,000 feet, the vertical speed changes from the steady climb of just under 600fpm to a negative 320 fpm in the next second.