In fact, back when smoking was allowed, minor fires started by cigarettes (often in trash cans) were so common that anything looking like that was not considered a very serious concern.

This led to the disaster of Air Canada flight 797, where an electrical fire near a toilet was mistaken for such a case, leading to a delayed response and a late emergency landing, the cabin already filled with smoke, so that 23 people died even though the plane had landed safely.