Many of the 210 passengers aboard the Jetstar flight from Gold Coast city on Sunday night had attended the Splendour In The Grass weekend music festival at Byron Bay and were returning home.
The male attendant was said to have told passengers via the Airbus A320's public address system: "There are sniffer dogs and quarantine officers waiting in the domestic terminal. If you need to dispose of anything you shouldn't have, we suggest you flush it now."
After the warning, passengers headed for the toilets.
A Jetstar spokesman said: "The crew member's words were poorly chosen and are plainly at odds with the professional standards we would expect from our team."