More airline tickets are being cancelled than new bookings made, according to the World Travel & Tourism Council, which warns the UK risks “increasing isolation”.
The WTTC said forward bookings for international flights “are lagging far behind the increased capacity generated by extra flights scheduled”.
“Data shows at the end of last month, there were more tickets being cancelled than new bookings being made,” it said.
Airlines had “dramatically” increased flights to popular holiday destinations, - many still on the government’s amber list - in anticipation of increased demand.
According to travel data firm Cirium, in the two weeks following the start of the traffic light system on May 17, scheduled flight capacity from the UK to Greece soared by more than 2,000%, with a 435% rise in flights to Spain, compared to two weeks before.
However, WTTC’s partner ForwardKeys found during the week of 14 May airline ticket sales from the UK to Greece fell 37%, while those to Spain fell 44% week on week.
Virginia Messina, WTTC senior vice president, said: “WTTC is calling upon the government to allow all those who are fully vaccinated, or can show proof of a negative Covid-19 test, to travel freely.
“We are seeing many countries, particularly those in the EU, allowing travellers that have been vaccinated or can show a negative test result, which will provide a boost to their economies in such a pivotal time.
“We should use our hard-earned competitive advantage from one of the world’s best vaccine rollout programmes, with nearly 40% of the population now fully vaccinated, to restore mobility and reopen the doors to safe international travel.”