Experts say debris fragments and sudden loss of fail-safe systems point to missile

To civil aviation professionals, including pilots, engineers and former crash investigators, there was something immediately puzzling about the crash of the Ukraine International Airlines passenger jet that fell burning out of the sky minutes after takeoff from Tehran.

Conversation on forums, and in a risk assessment that was rapidly produced by the organisations OpsGroup, pointed to the sudden and catastrophic nature of the event, including the loss of both communications and tracking systems.