A "nationwide issue" with e-gates at airports has been resolved after causing travel chaos across the country, the Home Office has said.
It said the system was back up and running and there was "no indication of malicious cyber activity".
Social media images and footage showed long queues at the passport scanning gates at several airports overnight.
Passengers also reported being held on planes after they landed, while others said the delays caused them to miss trains.
Heathrow, Gatwick and Stansted airports were affected, as well as Manchester, Bristol and Southampton, along with Edinburgh, Glasgow and Aberdeen.
One passenger at Stansted Airport told Sky News they had missed several coaches to central London because of the issues, and only cleared the airport after nearly three hours in line.
"Not much info given. No water handed out. Babies crying," they said.
Another at Luton Airport said it took around 80 minutes from leaving their flight from Amsterdam to get through border control.
One traveller said they were held on their plane at Stansted for around an hour and a half after landing.
"We weren't told much other than the e-gates were down but had no idea how long it would take," they told Sky News.
"After that not much was said other than we couldn't disembark till the other five planes ahead of us did."
'No indication of malicious cyber activity'
A Home Office spokesperson said:
"E-gates at UK airports came back online shortly after midnight.
"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."
E-gate system crashed last year
The disruption came after Border Force workers staged a four-day strike at Heathrow Airport in a dispute over working conditions last week.
The union said workers were protesting against plans to introduce new rosters, which they claim will see around 250 of them forced out of their jobs at passport control.
The UK's e-gates system also crashed in May last year, causing long queues and several hours of delays for passengers.
At the time travel expert Paul Charles told Sky News underinvestment in the UK's transport infrastructure had left these systems "hanging by a thread".
(c) Sky News 2024: 'No indication of malicious activity' as e-gates back working at UK airports after travel chaos<
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