The cause of a “nationwide issue” which led to long delays at airport passport e-gates on Tuesday remained unclear as the problem was resolved.
Heathrow, Gatwick, Edinburgh, Birmingham, Bristol, Newcastle and Manchester were among airports affected by the Border Force problem which causing delays with arrivals late yesterday.
Pictures and videos on social media showed long queues.
One passenger told the BBC he spent longer queuing for passport control than he did on a flight from Lisbon.
The Home Office, which oversees Border Force, said in a statement early today: “E-gates at UK airports came back online shortly after midnight.”
The problem with the automated passport gates. which use facial recognition technology. were first reported around 7.50pm, meaning the issue persisted for more than four hours.
A Home Office spokesperson told the BBC that “at no point was border security compromised, and there is no indication of malicious cyber activity”.
They added: “As soon as engineers detected a wider system network issue at 7.44pm last night, a large scale contingency response was activated within six minutes.
“At no point was border security compromised, and there is no indication of malicious cyber activity.”
The Home Office extended apologies to “travellers caught up in disruption” and thanked “partners, including airlines for their co-operation and support” during the outage.
However, Belfast International airport, which does not have e-gates, said Border Force “systems” had been impacted.
The problem echoed a failure of e-gates at major UK airports almost a year ago during the late May bank holiday weekend.
There are more than 270 e-gates in place at 15 airports and train stations in the UK.