The International Air Transport Association estimates up to 25 million jobs are at risk from the collapse of the travel market due to the coronavirus pandemic.
IATA director general Alexandre De Juniac said airlines will collapse if forced to refund all customers.
Airlines simply cannot afford to issue all refunds, and governments need to act fast to help carriers.
"The key element for us is to avoid running out of cash so refunding the cancelled ticket for us is almost unbearable financially speaking," De Juniac said.
He said about one-third of 2.7 million direct jobs in the airline sector had already been lost or were temporarily furloughed.
IATA said there is about $35 billion worth of tickets that are due for refunds through the second quarter.
The industry group has been pleading with governments to not force airlines to mandate cash refunds.
The US transportation department has ordered airlines to issue refunds for cancelled flights after a flood of consumer complaints.
This week a lawsuit was filed against United Airlines for refusing to pay a refund, and many more are highly likely.
