Phlarp's original comment was about 'a "Range Safety Officer" on the ground whose entire job is to determine if and when to deploy this self destruct system.'

Phlarp's original comment was about 'a "Range Safety Officer" on the ground whose entire job is to determine if and when to deploy this self destruct system.' The text I quoted implies there is an onboard flight termination system, even if there is no Range Safety Officer who can send external commands. FWIW, a part from an exploded rocket, like the engine, could still destroy a school bus filled with children. The odds are very hard to estimate, and made more complicated in that there are few failure modes where a rocket failure halfway across a continent, at supersonic speeds, would reach the ground without breaking long before.