[Talisker]

According to the NTSB, the very same air conditioning packs below the center tank, which helped make the vapor in the tank flammable by heating, would have been a viable target for a heat seeking missile.

It seems the engines would have been way hotter, though.

[Moonman62]

In my non-expert opinion I think an engine would be a more likely target, but the NTSB specifically said the air conditioning packs would have been a sufficient target, too.

[Swordmaker]

It seems the engines would have been way hotter, though.

The averaged position of those engines would have been center fuselage. At the speed of a Mach 2 missile, it would not have any time to differentiate between any and would select average center. . . which could be the air conditioner area.