Travel company Tui is set to shut 166 High Street stores in the UK and Ireland, affecting up to 900 jobs.
The UK's largest tour operator said it hoped to keep on 630 workers in a mix of sales and home-working roles and in remaining stores.
The decision was made after changes in customer behaviour, including a shift to online, the firm said in a statement.
About 350 retail stores will remain following the closures.
The outlets set to close have been chosen based on a number of factors, including local market data and "predictions on the future of travel", the firm said.
Tui said it will not release the list of stores at risk during the consultation period, but added that none of those that have reopened since lockdown will be shut.
"We want to be in the best position to provide excellent customer service, whether it's in a High Street store, over the telephone or online, and will continue to put the customer at the heart of what we do," said Andrew Flintham, managing director of Tui UK and Ireland.
"It is therefore imperative that we make these difficult cost decisions, look after our colleagues during such unprecedented uncertainty and also offer a modern customer service."
Tui also told the BBC that it had closed overseas customer services centres in Mumbai and Johannesburg in a bid to protect UK jobs.
The company announced in May that it planned to cut around 8,000 jobs globally as it sought to reduce overhead costs by 30% in a major restructuring.
But as the coronavirus pandemic has drawn on, the shift to online has accelerated.
"Customer behaviours have already changed in recent years, with 70% of all Tui UK bookings taking place online," Mr Flintham said.
"We believe Covid-19 has only accelerated this change in purchasing habits, with people looking to buy online or wishing to speak with travel experts from the comfort of their own home.
"We have world-class travel advisers at Tui, so we hope many of them will become homeworkers and continue to offer the personalised service we know our customers value."
Derek Jones, UK managing director of travel firm Kuoni, told the BBC that he believes the next six months will be "really tricky for the travel industry".
"Sadly, in my own business, we're having to make redundancies... but I think travel businesses in the long-term have a bright future," he said.
"And while I'm extremely positive and hopeful about the long-term, there is no doubt that the travel industry is heading for a very difficult period and that's why we're calling on the government for additional support."
The UK changed its advice after a spike in infections in some Spanish regions, including Catalonia, where Barcelona is located, and Aragon.