[Accujack]

A half ounce hex nut would take down a small airplane in the wrong place.

[iamaelephant]

A half ounce hex nut doesn't fly under its own power.

[Accujack]

It will if you attach an engine and fuel tank to it.

Or alternatively, a small bird in the wrong place can take down a plane. Or for that matter, a clog in the pitot tube from ice.