British Airways owner IAG is considering mounting a legal challenge to quarantine rules which are due to come into effect on Monday.
The dramatic move marks another sign of a breakdown in relations between the airline and the UK government.
IAG boss Willie Walsh told Sky News that airlines had not been consulted on the 14-day quarantine period for people arriving in the UK.
He said he expected other airlines to also mount legal challenges.
“We think it’s irrational, we think it’s disproportionate and we are giving consideration to a legal challenge to this legislation, so we’re reviewing that with the lawyers later on today,” Mr Walsh told Sky News.
“I suspect there are other airlines who are doing so, because it’s important to point out there was no consultation with the industry prior to enacting this legislation and we do believe it is an irrational piece of legislation.”
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Airlines and holiday firms have been arguing against a two-week quarantine period for anyone arriving in the UK that will be enforced from 8 June. Travellers to the UK will be required to isolate for 14 days or face a £1,000 fine.
The government has said that the period is needed to “keep the transmission rate down and prevent a devastating second wave” of coronavirus.
However, industry body Airlines UK has said quarantine “would effectively kill off air travel”.
The plans have caused friction between the government and British Airways. On Thursday the airline refused to attend a meeting with Home Secretary Priti Patel to discuss the quarantine rules.
British Airways is under huge financial strain due to the pandemic, and has said it is currently burning through its cash reserves at a rate of around £1m per hour.
Mr Walsh told Sky News that the Bank of England has loaned it £300m, which is the “maximum amount” available to it.
“We have done everything that is within our power to boost the cash balance of British Airways. We’re exhausting every single opportunity we can,” he said.
BA has faced heavy criticism from some MPs over a plan to slash jobs while accessing the government’s furlough scheme.
The airline has been under fire for plans to cut 12,000 jobs and weaken terms and conditions for its remaining staff.
It announced the redundancies just weeks after putting 30,000 workers on the job retention scheme which pays workers’ wages.
On Monday, a group of 200 travel companies wrote to Home Secretary Priti Patel asking for the plans to be scrapped.
The letter said travel could be possible for people – without quarantine – between destinations “deemed safe from coronavirus”.
The so-called “air bridges” would allow visitors from countries where coronavirus infection rates are low into the UK, without having to self-isolate.
It is understood that the government is working on a list of countries it is hoping to secure air bridge agreements with, which include all major European tourist destinations such as Portugal, Spain and France as well as Australia and Singapore.
However, the government’s official position is that the idea is “under consideration”, and not established policy.