Heathrow has started consulting with unions over pay cuts in a process which could lead to job losses.
The west London airport said in a statement that its proposal “guarantees a job” for anyone who wants to remain with the business.
Around 4,700 workers across engineering, air-side operations and security roles are affected.
Heathrow’s plan involves around half having their salary reduced by approximately 15-20%, the PA news agency understands.
If no agreement is reached, then job cuts could be implemented.
Heathrow has already reduced its managerial roles by a third, and in June launched a voluntary redundancy scheme.
The airport said in a statement: “Covid-19 has decimated the aviation industry, which has led to an unprecedented drop in passenger numbers at Heathrow, costing the airport over £1 billion since the start of March.
“Provisional traffic figures for August show passenger numbers remain 82% down on last year and we must urgently adapt to this new reality.
“Discussions with our unions have taken place over four months and our final offer is informed by feedback we have received from them.
“But with air travel showing little sign of recovery, these discussions cannot go on indefinitely and we must act now to prevent our situation from worsening.
“We have now started a period of formal consultation with our unions on our offer, which still guarantees a job at the airport for anyone who wishes to stay with our business.”
Heathrow has called on the Government to allow passengers arriving from countries not on the quarantine exemption list to pay for coronavirus testing on arrival, to give them the chance to reduce the 14-day self-isolation period.
Unite officer Wayne King said: “Heathrow Airport Ltd’s (HAL’s) actions are extremely unhelpful and further undermine confidence in the industry.
“Our members have worked tirelessly throughout the Covid-19 pandemic. To conduct industrial relations via the media in such a brutish manner is designed to create fear and panic in a group of key workers.
“HAL’s actions have made already difficult negotiations even more fraught.
“Unite is currently balloting its members on the proposals. HAL’s actions demonstrate that it is not prepared to allow democracy to run its course.
“At a time when Unite is working hard to persuade the Government to follow the lead of other European nations and provide specific financial support to the aviation sector to ensure that the industry and workers can survive the pandemic and thrive in the future, these actions are distinctly unhelpful.
“It should not be forgotten that HAL is an incredibly wealthy company. At the start of the pandemic it boasted of a £3.2 billion war chest. These attacks in pay are not about survival, but introducing measures to boost future profits.
“Unite urges HAL to withdraw this ill-judged attack on its loyal workforce and to return to the negotiating table as had been previously agreed.”