NHS Digital has said the issue which caused the NHS app and website to go down on Wednesday afternoon has been resolved.
The four-hour outage of England’s NHS app left scores of people unable to access their digital Covid vaccine passes earlier today.
Users attempted to download information required by many countries before flight departures - such as details about what vaccines they have had - but were prompted to "try again later".
It meant some people were not able to board flights as they were unable to prove they had been fully vaccinated.
After the IT wing of the NHS said it was investigating the issue, NHS Digital confirmed that the problem had been resolved at around 5pm.
In a tweet, it said the outage was caused by “a technical issue with a global service provider that affected many different organisations”.
The Covid Pass on the NHS app is used for people to prove they have recently tested negative for coronavirus before attending various events and venues.
And anyone hoping to travel abroad is likely to need to prove their vaccination status using the app before they are allowed to leave the country.
Foreign countries are also accepting the NHS app as a way for people to prove their vaccination or test status before entering venues.
Many holidaymakers' travel plans were disrupted by the technical malfunction.
Earlier today, Chuck Adolphy and his girlfriend were not allowed to proceed for an EasyJet flight from London Gatwick to Slovenia’s capital Ljubljana. “Went to go on the app and my Covid Pass wasn’t appearing,” he said. “Didn’t even realise at the time there was an outage was just turned away and told they couldn’t do anything about it. “Rang the number and they said the app and site are down and there is nothing they can do. EasyJet said nothing either. Showed them my vaccine card and nothing.” Callum Melia from Liverpool also said he was unable to access tourist attractions on his holiday in Naples, Italy, as a result of the app issue. “We’re about to enter these tours around the city when we discover we can’t get on the app to access the QR code,” the 26-year-old said.