Restoring Portugal to the UK's quarantine list for travellers would cause "further chaos and hardship", the head of British Airways' parent company has warned.
Willie Walsh, chief executive of IAG, criticised what he called an "ever-shifting list" of requirements, claiming the UK had "officially hung up the closed sign".
"Another U-turn by the Government, adding Portugal to the quarantine list, will cause further chaos and hardship for travellers," he said.
There were 21.1 positive tests per 100,000 people inthe seven days to 30 August, up from 19.4 for the week up to 29 August, figures show.
The UK's threshold for considering adding a country to its quarantine list is 20 or more cases per 100,000 people.
Ministers also take into account trends in case numbers, deaths, countries' testing capacities and whether any increase in infections is down to a contained outbreak or general transmission.
More from Covid-19
Chris Sainty, the British Ambassador to Portugal, warned "things can change quickly".
One airline has no seats left on flights back to the UK from Faro for the next three days.
Anyone returning from a listed country has to self-isolate for two weeks after entering Britain.
Taking issue with the UK's approach to quarantine, Mr Walsh wrote: "Healthy people shouldn't be locked up for 14 days simply because they have been travelling."
He also condemned the government's "blanket quarantine on travel from a staggering 160 countries".
Ministers have taken a "chaotic approach to quarantine", he claimed, writing in The Times: "France, but not Italy; Portugal and then not Portugal and the Canary Islands – hundreds of miles from mainland Spain."
He said this month's return to work was where "the rubber will truly hit the tarmac", and that the aviation industry was vital to Britain's economy.
He claimed that people "relaxing on holiday pose no more of a threat than someone catching a bus to the supermarket".
Turning to advice, Mr Walsh urged ministers to &quoRead More – Source