Or a jet could be struck by an asteroid. (TW800??)
A spark from a nicked or worn wire to an in-tank fuel gage occurred in the fuel-air mixture space over the fuel surface in a main fuel tank. At that moment this mixture happened to be explosive. By that I mean it more detonated, rather than burned.
Maybe 15 years before I was working on av fuel facilities. One day I idly opened a fuel manual for the different grades and types, say ten in all. Every one had a narrow band of a low percent of fuel vapor in the air that was explosive. Not so below that concentration, nor above. In winter you could be below that concentration in many cases. On a hot summer day it was a different story. You'd be above the the concentration on the ground there (MSL+30'), and a cruise altitude you'd be below the explosive concentration.
In those days, the military inerted that space with nitrogen. Civil aviation used sand-- they buried their heads in it. I recall thinking this was an accident waiting to happen. Fifteen years lateer, TWA 800 was in a climbout in the twilight of a summer day, I believe.
Asteroid? Are you kidding? You must be.
OE