TUI Group has pushed back the return of its operations in the UK into July.
The travel giant had hoped to begin offering holidays again on June 30th, but this has now been delayed to July 10th.
All trips planned in the interim will be cancelled as a result.
A statement said: “Due to the ongoing situation regarding Covid-19, the Foreign & Commonwealth Office currently advise against all but essential travel.
“We would like to extend a personal thank you for your patience and understanding as our customer service and social media teams work around the clock during such an unprecedented time.
“We have been working behind the scenes to make a number of changes to our processes.
“These changes will make sure that we are able to offer additional support to you going forward and will make managing your booking much easier for you.”
The Foreign & Commonwealth Office (FCO) currently advises against all non-essential overseas travel – though this has been the case since April.
On Monday, the UK introduced quarantine rules to further halt the spread of the coronavirus and lower the chances of a second wave of infection.
The new rules state that anyone arriving in the UK from abroad will be subject to 14-days in isolation, but they have been roundly attacked by the travel trade.