Heathrow Airport has apologised for disruption after the west London hub was hit by “technical issues”.
One passenger said the situation was “utter chaos” after a problem with the airport’s IT system saw staff called in to help passengers get to gates on the second day of the half-term weekend.
Heathrow confirmed the IT failure was affecting departure boards and check-in systems across all terminals.
British Airways, the biggest airline at Heathrow, has cancelled 20 flights.
In a tweet, Heathrow Airport said: “We are experiencing technical issues at the airport which we are working hard to resolve.
“To help direct customers to their gates, we have deployed additional Heathrow colleagues across our terminals.
“We apologise for the disruption and will continue to provide regular updates.”
Air traffic control is not affected by the technical failures, but the IT issues, which come on a busy day for family travel, have further compounded delays triggered by bad weather across the weekend.
British Airways said the cancellations were the result of Heathrow’s IT issues combined with the existing disruption caused by Storm Dennis.
It added that anyone on a cancelled flight would be entitled to a refund or could be re-booked. Overnight accommodation would be provided if necessary.
In response to a customer on Twitter, the airline wrote: “We’re aware Heathrow Airport is currently experiencing a technical issue that is impacting some of their IT systems across the airport, affecting a number of airlines.
“We are working with them to resolve the issue as a priority and apologise for the delay to our customers.
BA has experienced two high-profile IT failures in recent years.
In August last year, more than 100 flights had to be cancelled and a further 200 were delayed after an IT glitch involving two separate systems, one dealing with online check-in and the other with flight departures.
The airline also suffered a major computer failure over the spring bank holiday weekend in May 2017, which saw 726 flights cancelled and tens of thousands of passengers left stranded.