Edinburgh Airport was hit by an IT outage affecting airlines, media and banks around the world on Friday.
Passengers whose flights were cancelled were asked to leave the airport while teams managed waiting times “as best they can”.
Later in the afternoon, the airport said the backlog would last into the weekend but otherwise operations had returned to normal.
Cybersecurity firm Crowdstrike said the global IT issue was caused by a “defect” in a content update.
The Scottish government’s equivalent of Cobra meetings – the Scottish Government Resilience Room (SGORR) – has been activated to assess to assess any potential impacts across the country.
However, it confirmed that the government’s IT systems were working normally.
Departure boards at Edinburgh Airport’s terminal building appeared to freeze before 07:00, showing out-of-date information about gate numbers and take-off times.
A fire alarm also sounded, which was understood to be connected to the IT issues.
The airport said there had been 55 inbound and outbound flights cancelled throughout the day.
Passenger Ellie Jamieson, 22, was due to fly to Barcelona but told BBC Scotland News she had been waiting in a queue for more than an hour-and-a-half.
She said some passengers had been boarded onto their flight and removed again and police had blocked off the escalator.
Ms Jamieson said: “Airport staff are not explaining anything or giving any reassurance, just constant announcements saying there are technical delays.”
Scanners for boarding passes were down and had to be checked manually by staff.
Passengers are urged to check with their airline for flight updates over the weekend as there could be knock-on impacts from the outage.
Glasgow and Aberdeen airports said they had been largely unaffected.
However, multiple other airports in the UK and across the world reported delays, with many flights suspended.
More than 5,000 flights were cancelled across the world – 4.6% of those scheduled – according to the latest update from aviation analytics firm Cirium.
Ryanair said it was also experiencing problems and advised passengers to arrive at airports at three hours before their scheduled departure time.
Airports in Spain were also badly hit, leaving many UK holidaymakers stranded.
Corinne Morrison Gillies was in Alicante, waiting to fly home to Edinburgh with her mother Annette, 79, and 10-year-old daughter Ava.
The family were left on a coach with other passengers for over an hour-and-a-half before being taken to be manually checked in by airport staff in small groups.
Ms Morrison Gillies said: “All the flights are delayed and in red. There’s quite a bit of confusion and not a great deal of communication.
“They’re just trying to manage people as best they can at the moment. I feel for the older passengers here, I think they’re finding it more challenging.
Ticket problems
ScotRail said it had not been affected, but other UK railway companies and some NHS services reported problems.
NHS Shetland said issues had affected its fire alarm system and a medical practice in NHS Grampian has asked patients to only contact them with urgent issues.
One of NHS Borders patient management systems was also impacted and patients who have had appointments affected were urged to contact the health board.
There have also been reports of businesses being unable to process payments, with Morrisons saying some stores were affected earlier but that the issue had now been resolved.
The Royal Concert Hall in Glasgow also said it was experiencing problems in processing ticket bookings, and Heart of Midlothian football club said its ticket office was affected.
A Scottish government spokesperson said: “There has minimal impact on NHS services and patients should continue to attend all appointments as planned.
“There are no major outages reported for NHS Scotland systems.
“We are aware of impacts at Edinburgh Airport and would urge those travelling today to check with their operator.
“Impact is being experienced by a limited number of UK rail operators but at the moment ScotRail and the Caledonian Sleeper service is unaffected.”
Crowdstrike, which said a fix had been deployed, was founded in 2011 with the aim of safeguarding the world’s biggest companies from cyber vulnerabilities.
Its CEO, George Kurtz, said: “Crowdstrike is actively working with customers impacted by a defect found in a single content update for Windows.
“This is not a security incident or cyberattack.”
In a letter sent to its customers and partners, Mr Kurtz apologised for the global IT outage and says Crowdstrike “understands the gravity and impact of the situation”.