"The scale of the crisis makes a sharp V-shaped recovery unlikely. Realistically, it will be a U-shaped recovery with domestic travel coming back faster than the international market.
"Without urgent relief, many airlines will not survive to lead the economic recovery."
As of early April, the number of flights worldwide was down by 80 per cent compared to the same period in 2019, said IATA, which brings together 290 airlines.
The crisis began for the aviation sector at the end of January when airlines suspended services to China, where the Covid-19 virus outbreak began.
Since then IATA has repeatedly increased the estimated revenue losses as border closures have followed the spread of the new coronavirus around the world.
In its latest assessment, the association factored in longer-than-expected restrictions on international travel, and the virus spreading in Africa and South America.
De Juniac said that meetings with governments would start later this week to work up a plan to restart the sector, first by getting domestic flights going again, followed by regional and finally intercontinental routes.
"Monitoring the health of passengers will be a key element in this restart," he said.
Although he could not say for the moment what form that would take, he said there should be uniformity around the world to avoid a patchwork approach.
IATA is calling for airlines to be given financial relief in the form of loans, loan guarantees, support for the corporate bond market and tax relief.