Soon after boarding the overnight flight from Jakarta to Sydney, passengers on QF42 are being advised to "honestly" fill in their entry forms and declare to authorities if they had been on a farm, near animals, or had dirty shoes or clothing.

The "don't be sorry, just declare it" message was also repeated closer to landing at Sydney Airport.

"There is currently an outbreak of foot and mouth disease in Indonesia, including Bali," the in-flight announcement said.

"This is a highly contagious animal disease that affects farm animals such as cattle, sheep, goats and pigs.

"Australia is free of this disease. It's critical that you do not inadvertently bring it to Australia on your footwear or by bringing high risk foods and animal products.

"Now you must declare on your incoming passenger card, all meat, all dairy products, all dirty shoes and equipment and if you have been near animals or have visited rural areas.

"If needed you may dispose of items at biosecurity bins within the terminal.

"If you have dirty shoes or dirty equipment, please declare that to a biosecurity officer, who will help you.

"An outbreak in Australia would cripple Australian agricultural industries and would cost the Australian people many billions of dollar.

"We are very serious about preventing this devastating disease out of Australia.

"Serious penalties can apply if you don't declare truthfully on your incoming card.

"So please be honest as this is a potential threat. Thank you," the 75 second long announcement concluded.

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In the terminal, posters and flyers reminding travellers of the potentially catastrophic risk were also on display.

Passengers advising they had been on a farm were directed to a queue for further scrutiny, including if any meat or other food products were contained in their luggage.

Suitcases were opened and even dirt-free footwear was being decontaminated by quarantine officers.

- Mark Phelps travelled to Indonesia with AgCoTech.