Travelers bound for the UK are facing delays at passport control as e-gates are not functioning across the country.
The problem began on Friday night at airports including Heathrow, Manchester and Gatwick.
The Home Office said it was working with airlines and port operators to minimize disruption from the “nationwide border system issue”.
One union warned that queues would quickly form.
All airports across the country that use gates are affected, meaning people entering have to check their passports manually.
It is not clear what the problem is with the border system, with a Home Office spokesman saying it is “too sensitive to say”.
However, although it is technically affecting any place where people are checked into the UK, the impact is mainly being felt at major airports with e-gates.
This weekend was already expected to be busy for commuters, with the bank holiday coinciding with the half-term break for many families.
Passengers heading to the UK from Dover port also faced problems after the French passport system failed earlier on Saturday.
The problem has now been fixed, but cars and coaches have been waiting for almost an hour, with around 400 lorries queuing to make the crossing over a busy bank holiday weekend.
Airports around the UK issued statements warning passengers of delays but said they were working with the UK Border Force to ease disruption.
A spokesman for Gatwick Airport said queues had so far been “manageable” – although they were expecting 800 incoming flights on Saturday. It confirmed that the problem started between 19:00 and 20:00 BST on Friday.
The eGate system speeds up passport control by allowing some travelers to scan their own passports. It uses facial recognition to verify identity and takes a photograph of the passenger.
One passenger arriving at Gatwick said the situation was a ‘joke’.
Another, Craig Pullen, said he had to wait in line for more than two hours at Luton Airport on Saturday, adding that it was “very poor” that passengers were not regularly informed about e-gates or problems. The update was not being given. Told how long it will take to clear passport control.
Lucy Morton, from the Immigration Services Union, told JEE News that between 60 and 80 per cent of arriving passengers typically use e-gates, depending on the airport and because they are not available ” Very soon” queues are likely.
“There is no impact on national security,” he said, explaining that all arrivals will still be fully vetted by the Mend Officer Desk.
E-Gates can be used by UK citizens aged 12 and over and people from the European Union, as well as people from countries including Australia, Canada, the US, Japan and New Zealand.
But all entry points have mandated security desks for other passengers and those unable to use e-gates.
A Home Office spokesman said it was aware of “issues with the nationwide border system affecting visitors to the UK”.
“We are working to resolve the issue as soon as possible and are liaising with port operators and airlines to minimize disruption to passengers,” he said.
British Airways was also hit by IT problems on Thursday and Friday, affecting more than 20,000 passengers at Heathrow.
