The NHS Covid Pass, a digital record of individuals’ vaccine records, has become inaccessible – leaving British travellers struggling to board flights.

Users trying to access proof of their vaccination status via the NHS App and website on Thursday found that the service was unavailable, with the app telling users: “We are sorry the NHS Covid Pass is currently unavailable.

“At this time there is no alternative route for accessing this information via the NHS App or online.

“If you have already downloaded the information then your access should not be affected.”

On social media, several holidaymakers said they had been unable to check in at airports because they were unable to prove their vaccination status.

NHS Digital tweeted: “We are aware of issues with availability of the NHS Covid Pass. We are investigating this urgently and will provide an update as soon as possible.

“We apologise for any issues this may cause and appreciate your patience as we work to resolve it.”

The requirement for people to show the NHS Covid pass to visit indoor and outdoor events and venues, such as cinemas and nightclubs, was scrapped earlier this year.

However, it is still used as a way for people to show their vaccination status when travelling abroad to certain countries.

Jon May, 32, is supposed to be flying to Valencia from Bristol at 6am on Friday for a work conference – but when he tried to download his proof of vaccination on the NHS App on Thursday, which he needs to enter Spain, he found that it was down.

He said: “I’ve had all three jabs, and I went to the NHS App… and it said ‘Service unavailable’. I was like ‘what do you mean, service unavailable? I’ve got a flight at 6am.’”

Mr May, who works in marketing and is from Bristol, who does not have any other documentation to prove he has been vaccinated, said he is nervous that he will be detained at the Spanish border.

He said: “If it doesn’t work, I’m hoping they just go with it… I have had all my vaccinations, I just can’t get the certification.”

“I just don’t know what’s going to happen,” he added. “If they said it will be back up in six hours, or 12 hours, that would be fine – but I just don’t know what’s next… I might get to Spain and be deported from Spain, and that would be really embarrassing.”

Fi Bartlett, 24, from Bournemouth, is due to be travelling to Malaga on Saturday but was unable to complete her online check-in for her flight without proof of vaccination.

“There’s been no update from the NHS apart from to say they know it’s down,” she said.

“[The] flight is on Saturday early morning so we may be okay… if it’s still down I’m not sure what we’ll do – probably show up to the airport with our vaccine paper things we got when we were jabbed and hope for the best.”