Dozens of flights have been cancelled or delayed in the UK after an "extraordinary" communications failure grounded all planes across the US.

The UK's Civil Aviation Authority has warned of a ripple effect of disruption for passengers flying out of Britain after all flights in America were halted at about 9pm on Friday for "safety reasons".

The failure left millions of travellers stranded and caused chaos at airports in the UK.

Sean Duffy, the US transport secretary, said the nationwide "ground stop" – only the second since the 9/11 attacks – had taken place after America's air traffic control system was thrown into disarray by "old hardware".

He claimed the system had not been updated because of funding shortages caused by a lack of cross-party support.

At least 22 flights to and from Heathrow airport were listed as delayed on Saturday morning, while a total of 19 flights were cancelled, according to flight-tracking website Flight Aware.

A spokesman for the airport said most of its scheduled departures were running on time, but described the situation as "dynamic". They urged passengers to contact their airlines for further information.

British Airways said delays were expected, and a spokesman for Manchester airport said they were not experiencing any "significant" disruption but added that three flights to the US had been slightly delayed.

London Gatwick was expecting minimal disruption to its services on Saturday – with just one flight delayed so far – while three were delayed at London Stansted.

Aer Lingus, which operates out of Heathrow and Manchester as well as several smaller airports, said US-bound flights would be allowed to land but that those leaving America would be put on hold for now.

Virgin Atlantic said it was contacting passengers via email and text with further information.

"We recognise how disruptive this may be to our customers' travel plans and sincerely apologise for the inconvenience. Our teams are closely monitoring developments and working hard to minimise disruption wherever possible," the airline said.