It could take more than five years for international air travel to bounce back and countries enforcing quarantine periods aren't helping, the International Air Transport Association (IATA) says.
The IATA wants what it calls harmonised border controls - where countries collectively agree to rules aimed at protecting against Covid-19 - including temperature checks at airports, masks on planes and instant tests when they become available.
The association opposes mandatory isolation - such as the two weeks New Zealand enforces for travellers returning home from overseas - and maintains that conditions on a plane are safer than shopping at the mall or going into the office when it comes to the spread of Covid-19.
IATA Asia spokesperson Albert Tjoeng said the association had developed two scenarios for the future of air travel.
The first, optimistic scenario was one where domestic markets opened in the third quarter of the year, but it would be a lot slower for international markets.
"We don't expect 2019 levels to be exceeded until 2023. That's a couple years from now, and even by 2025 global passenger demand is still expected to be 10 percent below than what we had originally forecasted for the year in 2020..."
A more pessimistic scenario was that flight levels in 2021 would be 34 percent down from 2019 as a result of slower opening of economies and relaxation of travel restrictions.
"So, there are a couple of factors. One is confidence in travel. The other factor would be in terms of the stable economy," Tjoeng said.
"People will be concerned that if the economy isn't going to do well, then finances would be a consideration to determine whether or not they travel."
But quarantine measures were also a large deterrent, with the IATA's April survey of recent air travellers showing 86 percent were concerned about being quarantined while travelling and 69 percent would not consider travelling if it involved a two week quarantine period.
The association opposed mandatory isolation.
"Because if you're travelling and you're stuck in a quarantine compound for about two weeks, then, that really reduces any incentive to want to travel, which is why what we are proposing is to have a layered approach of biosecurity measures."
Those measures include screening at airports, vigourous contact tracing procedures, use of face coverings and masks, and other measures to reduce contact between passengers and crew.
Transmission on aircraft had been low in part because people didn't face each other when seated, Tjoeng said.