Airline industry bosses have urged Chancellor Rishi Sunak to extend his job retention scheme beyond June.
Aviation industry body Airlines UK said airlines hit by coronavirus would face "a renewed cash crisis" if the scheme were withdrawn prematurely.
The Treasury is currently paying most of the wages of nearly four million staff, working across the economy, who have been put on temporary leave.
Separately, an all-party group of MPs has called for a bailout of aviation.
However, the group of 20 MPs said in a letter to Mr Sunak that any support package offered to airlines and travel companies should come with stringent environmental conditions.
The letter said: "If public money is used to save them, they must be required by law to do more to tackle climate change.
"They must be obliged to follow in the footsteps of many in the industry that have implemented ambitious carbon offsetting schemes."
On Sunday, Virgin Atlantic said it was still in talks with the UK government about a coronavirus-related bailout.
Many airlines have been struggling as revenues have dropped amid travel bans.
'Cliff edge'
In its own letter to the chancellor, Airlines UK said it expected that once coronavirus restrictions were eased, the return to normality for international aviation would be "gradual rather than sudden" and that carriers would increase capacity "incrementally".
Airlines UK said that it believed the job retention scheme would need to be extended beyond June. It said the government should consider "tapering" the scheme or reviewing it on a sector-by-sector basis.
Otherwise, it said, aviation would be "facing a cliff-edge post-June, whilst services are scaled up".
The job retention scheme was originally intended to cover 80% of furloughed workers' wages for March, April and May, but has since been extended until the end of June.
According to the UN's civil aviation body, ICAO, international air passenger traffic in the first three quarters of 2020 could drop by as many as 1.2 billion travellers, or by two-thirds.
Many in the airline industry believe it could take up to three years to get back on track. However, last week Ryanair boss Michael O'Leary said he expected to see a much faster recovery, subject to an effective coronavirus vaccine.
Source: BBC