I wonder whether the Cellon dope caught fire first. It's highly flammable and unstable.

From another article, about a 1916 German bomber .. https://eandt.theiet.org/content/articles/2017/11/eccentric-...

> First, Cellon, a type of cellulose acetate, was highly flammable, which, combined with the wooden fuselage, made the plane a tinderbox. Secondly, it wasn’t very strong or stable; in dry weather the material shrank, warping the wooden fuselage, while in damp weather it expanded and made the whole structure sag. This had a very unnerving effect in flight, as the control surfaces changed characteristics from moment to moment depending on humidity. Cellon also decayed in ultraviolet light, becoming yellowed, brittle and prone to explosive shattering.