The trade association for the world's major airlines is proposing a range of measures aimed at relaunching the global air travel industry -- including an end to in-flight physical distancing rules -- that run counter to the established policies of Canadian airlines and the federal government.

The International Air Transport Association's roadmap to restarting commercial flights -- which have dropped off by more than 95 per cent among Canadian carriers due to the COVID-19 pandemic -- suggests that passenger face coverings have "obviated" the need for social distancing on board, that aircraft seats provide a further barrier to viral transmission and that onboard air filtration systems are equivalent to those at hospital operating theatres.

Nonetheless, the trade group backs a ban on washroom lineups to reduce "congregation of passengers" in the cabin.

"If we don't take these first steps in a harmonized way, we will spend many painful years recovering ground that should not have been lost," said IATA director general Alexandre de Juniac.

IATA's other proposed in-flight measures include pre-packaged meals to reduce interaction between passengers and crew and frequent "deep cleaning" of the cabin. But even with those precautions -- already in place at most airlines -- packing passengers into a plane is "really inviting disaster," said Tim Sly, epidemiologist and professor emeritus at Ryerson University's School of Public Health.

"That's bad enough, putting 250 people in an aluminium cigar tube, all elbow to elbow breathing the same air for two, three, four, five, 10 hours," Sly said in a phone interview.

He conceded modern airplanes have "a heck of a filter system built in," but said masks alone cannot prevent the on-board spread of COVID-19.

"I think we have to be very, very careful," he said, "unless the people sit there with almost a hazmat kind of set-up...connected directly to the air supply above."

Safety and health authorities have stressed physical distancing on land and in the skies since the outbreak began.

Transport Canada listed social distancing among the "key points" in preventing the spread of the virus as part of a guide issued to the aviation industry last month.

"Operators should develop guidance for spacing passengers aboard aircraft when possible to optimize social distancing," the document states.

Air Canada and WestJet Airlines Ltd. -- both of which the association counts among its 290-odd members -- say their pandemic policies block the sale of adjacent seats in economy class or throughout the entire plane.

"The middle seat on our Boeing 737s and 787 aircraft and every other seat on our Bombardier Q400 has been made unavailable to book to ensure our guests and crew can continue to fly safely and have more space to adhere to social distancing guidelines," WestJet spokeswoman Morgan Bell said in an email.

The policy is in place until June 30, "and we will re-evaluate this initiative as required," she said.

In its proposal -- titled Biosecurity for Air Transport: A Roadmap for Restarting Aviation -- IATA recommended temperature screening by government staff at airport points of entry before departure and, if required by authorities, upon arrival.

Temperature checks' effectiveness remains disputed as the virus may still be in an incubation period or manifest only mild symptoms when an individual is scanned.

"The more you actually understand this virus, the more you begin to know that temperature-taking is not effective at all," Dr. Theresa Tam, Canada's top public health official, said earlier this month.

"Even if you are infected, we know that the likelihood of picking up someone who is symptomatic is relatively inefficient," she said.