FWIW, sodium in water is such a pathetic explosion that it would mostly be an embarrassment for the would-be bomber. It wouldn’t do any meaningful damage.

An explosion with real gravitas is far more difficult to execute than people imagine. (see also: people that think ANFO is a viable explosive) This goes a long way in explaining why truly destructive bombings are rare.

Airliners are also pretty robust against damage. Although they are not designed to resist explosions, everything is redundant.

This robustness is why fighters in WW2 used cannons for guns. Poking a hole in the side won't do anything.