The incident occurred on a Virgin Australia on Sunday.
A passenger told KCAL9's Laurie Perez that the flight was only a few minutes in when he heard a "pop."
He said the cabin was then filled with the worst kind of stench. Others took to Twitter to describe the incident.
Three hours in, the pilot eventually turned the plane around.
"It was a vile smell. It smelled like chemicals, excuse me, mixed with vomit and excrement and very acidic," John Collins, a passenger, told Perez in a phone call from Australia Tuesday night.
Collins says a stream of liquid buckled into the carpeting.
He took a dim shot of the mess and of the bathrooms that had been cordoned off.