Iron oxide
Proponents of this hypothesis argue that the coatings on the fabric contained both iron oxide and aluminum-impregnated cellulose acetate butyrate (CAB) which remain potentially reactive even after fully setting. Iron oxide and aluminum can be used as components of solid rocket fuel or thermite. For example, the propellant for the Space Shuttle solid rocket booster included both "aluminum (fuel, 16%), (and) iron oxide (a catalyst, 0.4%)". The coating applied to the "Hindenburg"s covering did not have a sufficient quantity of any material capable of acting as an oxidizer, which is a necessary component of rocket fuel, however, oxygen is also available from the air.