Many people are hesitant about travel solely due to the unpredictable rules and restrictions which have the potential of turning one's trip into a dreadfully expensive logistical nightmare. Fear of infection is no longer the driver of most people's decision to postpone a trip until better times. A sizable fraction of the usual travelling public in the developed world has been lucky enough to get vaccinated. Many survived COVID. Some simply aren't afraid of it because their individual risk assessment does not perceive it as an existential threat (spoiler: those are mostly young, healthy individuals who don't have anyone old or infirm around them). As long as you give those people reassurance that the rules are unlikely to change overnight, they seem to be more than happy to grab a "green pass" and jet off. That's precisely what the EU COVID certificate did. A mere week after its introduction, traffic is already at above 60% of 2019 levels. Following the big announcement regarding the cancellation of quarantine for amber list arrivals to the UK from 19th July, it can easily hit 70% by August. Remember that last summer it barely reached 45% of 2019 levels. That's quite an improvement.