Electronic passport gates at UK airports have failed, causing chaos at London's Heathrow where long queues filled immigration halls and some passengers were detained on aircraft until space inside was available.
The UK interior ministry said a technical issue had affected e-gates at a number of ports of entry.
"The issue was quickly identified and has now been resolved," it said in a statement on Friday.
One passenger at Heathrow said it was chaos in the terminal, with space to queue rapidly running out.
The e-gates are staffed and operated by the UK's Border Force, a department of the interior ministry.
Passengers at Heathrow had already endured lengthy queues this summer as staff struggled to process COVID-19 documentation in addition to passports and visas.