Several times, my flight has been delayed when passengers don't make it to the gate in time and then (after a long wait) the baggage-handlers have to go into the holds and manually find the bags to offload.
First, is this a legal requirement? Do all carriers follow this same practice?
If so, then why is this a security risk any greater than the same flight anyways carrying air-cargo in its hold? Flights do that, correct? Not all cargo space is filled with checked-in baggage?
Does anyone know the rationale behind this calculation? If the hold anyways contains unaccompanied cargo then why treat unaccompanied passenger baggage as a high risk?
Also, historically, is there a record of such offloaded bags (for missing passengers) actually turning out to be containing explosives?