Public health experts are divided on whether plane passengers should wear face masks on board, with all three Australian airlines adopting a different policy on the matter.
Qantas and Virgin are increasing flight schedules as thousands of passengers take to the skies ahead of the school holidays. Both airlines supply passengers with optional masks, while Regional Express forces passengers to wear them. Australian government health advice remains that masks are optional.
After months of warnings to remain physically distanced from strangers, the spectre of full flights results can be a contronting contradiction. Despite restaurants, trains and workplaces adhering to the four-square-metre rule, commercial flights remain full as airlines fill middle seats to ensure flying remains financially viable.
Aircraft manufacturer Boeing says cabin air gets circulated and cleaned every two to three minutes. Air enters the cabin above each passenger and flows down vertically before evacuating the plane via ducts at passengers' feet. The air entering the cabin is a mixture of fresh outside air and recycled air. High-efficiency particulate air (HEPA) filters clean the recycled air, with Boeing claiming 99.9 per cent of bacteria and viruses are removed.
Despite this, University of NSW epidemiologist Mary-Louise McLaws says airlines should "definitely" make masks mandatory onboard flights.
"They seem to think the HEPA filter is this panacea," Professor McLaws, a member of the World Health Organization's expert panel on COVID-19, said.
"HEPA filters were designed for an infectious disease [hospital] ward where someone was infected to remove viral particles so any staff without personal protective equipment in another ward or another corridor would be safe," she said.
"[Nurses] do not stand in that ward without a mask… they still wear a mask."
Professor McLaws said despite the comparably low prevalence of COVID-19 in Australia, wearing a mask on planes is good risk mitigation when physical distancing is not possible. Without face protection, airplane cabins were possible "super spreading" environments, she said.
"Lots of people, a small area, for a long period of time. It's a perfect storm."
Passengers wear masks on board a full JAL flight from Bangkok to Tokyo. Photo: Getty
Professor McLaws said the contradiction of full flights despite other restrictions is "very confusing for the public - no wonder they then socialise and you have cluster outbreaks because they're receiving a mixed message".
But Professor Lyn Gilbert, who chairs the Infection Control Expert Group that advises the Australian Health Protection Principal Committee, does not think masks are necessary on board flights.
"That's been a great source of controversy and anxiety," she said.
"We've said in the context of Australia at the moment with low community transmission there's no particular benefit and potentially considerable harm. Wearing a mask is not harmful per se, but can give a sense of security that means that other more important precautions are more likely to be neglected – especially if the mask is not used correctly, as it often isn't."
Professor Gilbert said making masks mandatory was also problematic because it meant enforcing the measure.
"There's a feeling if you wear a mask you can get out and about but we really want to discourage that - physical distancing is the real issue we have to keep hammering."
Professor Gilbert said she would "probably not" wear a mask on board.
"I think it would be hypocritical if I did – but I would not be flying unless it was really essential."
Despite the Australian aviation industry agreeing to a joint framework for air travel, each Australian airline has a different policy.
Virgin Australia makes masks "available" to any passengers who want one but stops short of recommending them. A spokesman said: "Cabin crew are also able to use as they wish and at times where appropriate distancing is unable to be maintained."
Qantas and Jetstar provide passengers with face masks and recommend they be worn. Cabin crew are also provided with masks but they are not explicitly recommended to wear them.
Qantas chief Alan Joyce wears a face mask on board a flight. Photo: Supplied
Meanwhile Regional Express forces customers to wear masks onboard, either one they brought with them or a supplied one for $2 at the check-in desk.
As Boeing scrambles to restore the public's confidence in flying, the aircraft manufacturer recommends everyone onboard wear masks.
"If you're sitting next to a passenger and that passenger coughs or sneezes, that cough won't immediately go through the HEPA filter. It has to get down through the floor and out," Boeing's product marketing director Jim Haas told this masthead. "So really wearing masks is part of our social responsibility to protect our fellow travellers."