Thousands of passengers whose flights were cancelled due to the global IT outage are being asked to leave the overcrowded airports.

About 167 flights scheduled to depart from UK airports were cancelled, others were delayed, while 171 flights scheduled to land in the UK were cancelled due to the technical glitch.

At airports such as Gatwick, Luton and Manchester, passengers had to wait long times at check-in counters and pass through security checks.

Aviation analytics firm Cirium said 5,078 flights worldwide – or 4.6% of scheduled flights – were cancelled on Friday, including 167 departures from the UK.

Ryanair, which said it was “forced to cancel a small number of flights today”, told passengers: “If your flight has been cancelled, we kindly ask you to leave the airport as we are currently unable to assist passengers at the airport due to the IT outage.”

Edinburgh Airport said: “Anyone whose flight has been cancelled is asked to leave the airport and contact their airline directly.”

Transport Minister Louise Haigh said her department was “working closely with industry and all government representatives on this issue”.

A traveler at Gatwick Airport said he waited in line for more than three and a half hours before his flight to Miami, Florida.

Dean Seddon, 42, from Plymouth, told the PA news agency: “There are just people everywhere. There must be 400 people in the queue at the check-in desk where I am standing… it’s just a madhouse.”

Lance and Penny Spraggons said they waited in a check-in queue at West Sussex Airport for more than an hour.

Mr Spraggons said: “The biggest problem is the lack of information.”

The queue at Stansted snaked along in front of the main terminal building.

Courtney Kemal, 32, who had already been waiting in line for about two hours in the late morning, said her two sons, aged five and seven, were “obviously stressed”.

Rory Boland, editor of Which? Travel magazine, said passengers travelling today “will naturally be deeply concerned”.

He continued: “Avoid checking a bag if possible, as airport check-in queues are long and IT outages typically result in a lot of baggage being lost.

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“When checking baggage, make sure that medications, keys and other important items are in your hand luggage.”

He said passengers were not entitled to compensation for delayed or cancelled flights due to “extraordinary circumstances”, but airlines had a duty to look after them, including providing meals, accommodation and, if necessary, alternative flight bookings.

British air traffic control provider Nats said its systems were “functioning normally”.

With 3,214 departing flights, Friday is the busiest day of the year for UK air traffic as thousands of families head off for the summer holidays at the end of the school year at many schools.

Several US airlines suspended flights, including United, American Airlines and Delta.

The train information website National Rail Enquiries warned passengers of “widespread IT issues across the network”, although most trains were running as scheduled.

South Western Railway said all ticket machines had stopped working due to IT problems.