Chaos ensued at several UK airports after a technical outage affecting passport control e-gates caused long serpentine queues on Tuesday evening.
E-gates are automated gates that use facial recognition to check a person's identity and allow them to enter the country without talking to a Border Force officer.
There are more than 270 of them in place at 15 air and rail ports in the UK, according to the government's website, which also says they are supposed to "enable quicker travel into the UK".
Major airports including Heathrow, Gatwick, Edinburgh, Birmingham, Bristol, Newcastle, and Manchester all confirmed problems with passengers being processed through the border on Tuesday evening causing delays.
Videos doing the rounds on social media showed large queues of passengers waiting at passport control.