British Airways passengers have been left concerned for their safety after it emerged that some flights are running with '70% capacity'.
Passengers have complained about packed flights and people travelling without masks, amid fears of a second peak of the virus.
BA said face masks are a "personal preference", adding that it is currently in talks over how to implement safety procedures in a post-coronavirus world.
Under current rules, the airline said facial coverings are not compulsory on board its flights.
The aviation industry as a whole is struggling to bounce back from the coronavirus pandemic, with Virgin Atlantic, British Airways and easyJet all facing significant losses after a season of cancellations.
British Airways has already announced plans to lay off 12,000 staff, while dozens more have told The Mirror they're being forced to accept pay cuts.
Operators are also struggling to devise ways to ensure social distancing on flights while carrying enough passengers to ensure the survival of their business.
Ryanair previously said flights would not resume if middle lanes had to be kept empty. In one suggestion, boss Michael O'Leary said the Irish Government should foot the bill to help keep the airline proftable.
BA said its transatlantic flights are quiet enough to ensure social distancing.
But that has not stopped passengers taking to social media to complain about packed BA flights on the continent with passengers seated directly next to each other and without face masks.
The UK has not issued guidance for airlines but the European Union Aviation Safety Agency said passengers should be 1.5metres apart and wear masks.
Passengers arriving in the UK will also be required to quarantine for 14 days under strict restrictions introduced by the government.
A spokesperson for British Airways said: "We follow all the guidance from the UK Government and global health authorities, including Public Health England and the World Health Organisation.
"We have taken several steps to greatly reduce contact between customers and crew, and personal protective equipment is available to them.
"Like other forms of transport we are keeping vital links open - repatriating customers and ensuring key supplies like medicines and food are flown in. Our teams are doing an amazing job.'
Twitter user Jonathan Gitlin posted images of a packed BA flight from Amsterdam with passengers not wearing masks.
He accused the airline of "squeezing passengers in".
British Airways responded to the tweet by saying: "Hi Jonathan, I know this is worrying for everyone, but I'm afraid its personal preference whether our passengers want to wear a mask or not on board?
"If I can help with anything else, please feel free to come back to us."
Another Twitter user from Copenhagen replied that it was a similar story in Europe, as he tweeted an image of a full flight, although this time every passenger was wearing a face mask.
"Yeah they're all doing it. Here in Europe too, though it seems wearing a mask is mandatory now. It wasn't a few weeks ago," he wrote.
Another woman claimed she was refused an empty seat despite there being availability on board.
"This is social distancing on British Airways.... when I asked if I could move I was told I can’t sit in the empty aisles due to weight issues on the plane. Isn’t corona an issue?!" she wrote.
British Airways has said it is looking into updating its safety and social distancing measures for when flights resume in July.
Social distancing will be encouraged, but the airline will not require seats to be kept empty.
It follows in the footsteps of easyJet, Ryanair and Jet2 who have all vowed to resume flights this summer amid a huge profit hit.
Easyjet has announced plans to keep the middle seat in empty within banks of three seats to ensure social distancing on its flights.
Passengers will also be required to wear masks. .
BA sources told The Sun that a flight from Amsterdam to Heathrow yesterday was at around 70% capacity.
"BA seems to have taken a decision not to bother even trying to social distance passengers. Crew are not wearing masks or gloves on-board," a source told the publication.
The European Union Aviation Safety Agency recommends social distancing of 1.5m 'where possible', with check-in and boarding altered to avoid passengers congregating.
While passengers should be encouraged to wear masks during the journey, the guidelines stop short of requiring people to wear them.
"Aeroplane operators should ensure, to the extent possible, physical distancing among passengers," the terms state.
"If physical distancing cannot be guaranteed... passengers and crew members should adhere at all times to strict hand hygiene and... should wear a face mask."
