What event would kill most of the worlds population at the SURFACE, but spare everyone at the altitude of a commercial jetliner?

I want a realistic event to occur that kills the majority of the Earth's population. However, the nature of this event must not effect humans or machinery currently flying at high altitudes (those of passenger airplanes).

The event can be singular or be multiple events occurring simultaneously around the globe.

It should also be unexpected -- commercial airlines would likely be prohibited from flying if threat of nuclear war was escalating (and then acted on while the airline is in flight).

Natural disasters are not quite relevant because they cannot match the cataclysmic scale of wiping out everyone on the surface simultaneously.

posted almost 8 years ago

socrates‭

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