Heathrow, Gatwick and Edinburgh airports all reported long queues at the UK border on Friday afternoon as e-gates across the country went offline.
Border Force issued a statement saying IT issues were affecting e-gates nationwide and that all available staff were working to process arrivals.
Some passengers reported being held on planes due to long queues at passport control.
There are over 270 e-gates in place at 15 air and rail ports in the UK, intended to enable quicker passage into the UK. British nationals, EU citizens, and citizens of countries including the USA, Canada and Australia can use them.