Holidaymakers are jetting out of the country as a ban on overseas leisure travel is lifted.
Thousands of people are expected to take to the skies as travel restrictions are eased in England and Wales on Monday.
The relaxation of the rules was described as a “symbolic moment after the most difficult year in our history”, by one airports chief.
Travel firms have reported a surge in demand for trips to Portugal, after the Government put the country on its green list for travel meaning travellers will not need to self-isolate on their return, and are only required to take one post-arrival test.
EasyJet has added 105,000 extra seats to its flights serving green-tier destinations, while Tui will use aircraft which normally operate long-haul routes to accommodate the surge of people booked to fly to Portugal.
Manchester Airports Group chief executive Charlie Cornish said: “Welcoming passengers back to our airports today is a symbolic moment after the most difficult year in our history.”
The group owns and operates Manchester, London Stansted and East Midlands airports.
While Mr Cornish hailed the resumption of international travel as an “important milestone”, he said the limited green list is “not the broader restart our sector or our passengers were hoping for”.
Only a dozen countries and territories are on the green list but most are either remote islands or do not currently allow UK tourists to enter.
Mr Cornish called for a “smarter approach to protecting the UK from variants of concern which would remove the need for costly PCR testing”.
He added: “This big step forward would recognise the scientific evidence which shows that vaccinations, and the effective use of testing, can support safe travel to a much larger group of low-risk countries.”
The Government is advising people not to make non-essential trips to locations on its amber list, which covers popular destinations such as Spain, France, Italy and Greece.
But this guidance is expected to be ignored by some holidaymakers.
Health Secretary Matt Hancock said people should not travel to amber or red list countries “unless it’s absolutely necessary, and certainly not for holiday purposes”.
He told Times Radio on Sunday: “The red and amber list countries are places that you shouldn’t go to unless you have an absolutely compelling reason.”
Those who do travel will be required to self-isolate at home for 10 days on their return, and take two post-arrival tests.
They can end their quarantine early if they receive a negative result from an additional test taken after five days.
Travel firms such as airlines and tour operators have called for quarantine and testing requirements to be relaxed, and for more destinations to be added to the green list.
But Sir John Bell, regius professor of medicine at Oxford University, cautioned that there are “broad swathes of Europe that are largely unvaccinated” and are therefore “pretty vulnerable to new variants, be it Indian or otherwise, sweeping across the continent”.
He advised that travel abroad is therefore “not a good idea” at the minute.
He told Times Radio: “We aren’t at the peak of this thing globally at all yet, we’re still going up the mountain. So having people flying around and coming back with whatever local variant they run into, that is not a good idea in my view.
“I think people just have to get used to the fact that Cornwall or Bournemouth or wherever is not so bad. And they should just enjoy the summer and then we can get back to this properly when things settle down.”
Chair of the Commons Home Affairs Committee Yvette Cooper said there must be a “better approach to borders” amid the threat from new variants.
The Labour MP called for weekly assessments by the Joint Biosecurity Centre of case rates and the risks of new variants from different countries to be published, saying this would mean ministers could “act fast on a precautionary basis”.
Urging improvements to border testing and quarantine, she wrote in The Independent: “Time and again we have seen similar mistakes and delays in
acting on Covid at the border.
“Lessons must be learned or it will happen all over again.”
The Government has pledged to update its lists on June 7, and will review its overall policy in relation to arriving travellers on June 28.
Scotland will permit foreign holidays from May 24.
Non-essential travel from Northern Ireland to the Common Travel Area – which consists of the UK, Republic of Ireland, Channel Islands and Isle of Man, will be allowed from the same date.