Airlines receiving state support would be barred from paying dividends or buying back shares until at least a year after the cash is repaid, while "all elements" of executive pay would be capped.

Support would only be granted where an airline is suffering losses or seeking to consolidate its operations, or where it is either providing – or committed to replacing – vital connectivity that has been, or would otherwise be, lost.

Workforce reductions, meanwhile, would be capped at 10% or less, and employment and employee terms would be protected. Airlines seeking support would also have to commit to transitioning to "more efficient, greener travel operations".

Unite, which represents more than 60,000 workers in aviation, has written to chancellor Rishi Sunak and transport secretary Grant Shapps setting out its vision "to secure the long-term viability of the UK aviation sector".

General secretary Len McCluskey said the reforms should form parter of the government’s "previously promised, but as yet undelivered, government aviation package", hinted at by Sunak in his first round of emergency coronavirus support set out on 17 March.

Citing "industry bodies", Unite does not believe aviation will return to "anything like normal" until the second half of 2021, and that passenger numbers may only eventually recover to 90% of pre-coronavirus levels.

"A decline in such numbers would in that period make many flights and carriers uneconomic under the current aviation model," said Unite.

"Unite believes to have a viable future, and to meet climate challenges, it is inevitable the industry must change and that there could be wider scale consolidation across all parts of the sector and for this to occur the government will need to initially provide finance," said the union.

Unite wants "crucial sectors" of the aviation industry such as airports, airlines and air traffic control, which it says constitute part of the UK’s basic infrastructure, to be protected.

McCluskey said the government’s furlough scheme was an "excellent first step" but warned "further radical action" would be required to secure the future of the UK’s aviation sector.

“As an island, aviation is crucial to the UK for trade, business and maintaining social and family networks," said McCluskey. "During the Covid-19 pandemic, aviation has continued to play a vital role delivering critically needed supplies, such as medicines, as well as repatriating citizens from around the world.

“We know the Treasury and the government is rightly looking at the shape of the economy on the other side of this crisis and Unite hopes it will appreciate the union is acting as an honest broker whose concern is protecting jobs [and] the economy, not shareholders and the boardroom.

“What is clear is the UK aviation sector will not simply fully restart once the lockdown ends and if we are to have the viable industry the UK needs and which provides hundreds of thousands of jobs, further radical action is required.

“The UK’s aviation sector can and will have a viable future but it is going to look very different to what existed prior to the pandemic. The government has a key strategic role in shaping the future of what is and should remain, a world-class sector."

Unite’s key demands include:

• Government having the ability to provide loans and/or take a financial stake in companies. All loans and stakes to be fully repayable;
• Any companies participating in such a scheme would be prohibited from paying dividends, undertaking share buybacks or capital contributions, until 12 months after the loan is fully repaid;
• Participants will be required to call ’all elements’ elements of executive pay;
• Protecting employment and employee terms and conditions, with any reduction in workforce restricted to 10% or less;
• Ensuring eligibility extends to companies suffering losses or acting to consolidate business; or to rescue or replace a part of the sector that no longer exists;
• All financial support and loans be provided on the condition recipients have a clear programme of transition to more efficient and greener travel operations;
• Publicly financing smaller airports and air traffic control, as well as specific routes within the UK’s aviation network, to retain much-needed and vital connectivity