The clues emerging so far about the final moments of Metrojet Flight 9268 don't paint a clear picture of what happened to the doomed passenger jet.
Was a midair heat flash that a U.S. satellite detected over the Sinai Peninsula when the flight went down a sign of an explosion aboard the plane? And if that was the case, why haven't investigators found signs of an explosive impact on the crash victims' bodies, as Russian state media reports? Could the plane's wreckage show that a past repair went awry?
There are a wide range of theories on what made the passenger jet plunge to the ground, killing all 224 people on board, but Russian officials say it's too soon to speculate on the cause.
Aviation experts agree, and officials have downplayed an apparent claim by Islamic militants that they brought down the Airbus A321-200, saying technical failure is the most likely reason for the crash.