Reichstag Fire: 102 minutes that changed America

It depends on how much you have of it

It is denser than lead though

Yes, and although early 747s used it for aileron and elevator mass balance weights it was phased out and replaced with other dense material.

When the Korean Air crash near Stansted happened, there were concerns over the mass balances burning and uranium being blown about in the smoke. It was an early airframe which did used it.

Years ago at GEC we had an APG-65 radar scanner delivered to us, when the safety officer discovered it used DU counterweights he went ballistic and insisted that they be removed as it was a fire hazard. I forget how it was resolved now, but I do remember than when the weights were removed the four bar scan no longer worked as the motors and gearboxes simply couldn't control the antenna position correctly.

Most heavy metals are pretty poisonous.

Lead, plutonium, uranium. Irrespecteive of any radiation issues.

Yes indeed. But two of those are very keen to burn, whereas lead is much harder to ignite. Other heavy metals may not be, I don't know them well enough to be sure.

indeed, the problem with DU in planes isn't the radiation, it's the poisonous gases given off when it burns.

AIUI tungsten and other dense metals are more toxic when burnt.

DU has other uses too, like radiation shielding.

Or the BBC.