By Joseph Lee & Simon Browning
image copyrightCamilla McMynimage captionPassengers reported long queues and a lack of information at Stansted Airport
Airlines and airports say they are having their busiest weekend since the pandemic began as schools close and the summer holidays begin for millions.
Heathrow Airport expects 60,000 passengers to depart daily, while Gatwick says it expects 250 flights a day - up from a low of just 15.
But the numbers are still far below pre-pandemic levels.
Spain is the top destination for UK travellers, followed by Greece.
After 18 months in which the travel industry has been devastated by the pandemic, companies including EasyJet, TUI and Jet2, as well as major airports, said they would have more passengers this weekend than at any time since the pandemic began.
Air travel companies said the decision to let fully vaccinated travellers visit amber list countries without quarantining on their return had encouraged people to consider more destinations.
Travellers at London Stansted Airport in Essex reported snaking queues at check-in and security - with one passenger telling the BBC they felt it was "chaos" with staff overwhelmed.
Camilla McMyn said some passengers were upset after missing flights due to the long queues. "I haven't been crammed up next to so many people for a long time," she added.
Some 1,330 flights were due at Stansted between Friday and Monday, up from 735 during the same weekend in 2020.
Manchester Airport said it was "an encouraging but tentative step towards recovery", but it said the government's "chaotic and unpredictable" approach to international travel had damaged confidence.
EasyJet suggested the vaccination programme had given the travel industry a boost, with many Britons saying they were much more likely to want to travel once they had been double-vaccinated and that travel had been a major motivation for getting jabbed for many of them.
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