Falling waste? What actually happens when you flush the toilet on a plane

The loud 'whoosh' of an aircraft toilet is an air pressure vacuum.

The rumbling of the toilet flush on board an aircraft is so disconcerting it sparked an urban myth that the bowl contents and passenger could be ejected into the sky.

For many, a trip to the bathroom during a flight is escapable and the unusual signs stuck on the lavatory walls probably raise several questions. For starters, why is the flush so loud? And why can’t you flush while seated?