Global airports including Singapore's Changi hit by cyber outage

In Edinburgh, a Reuters witness said boarding pass scanners carried a "server offline message", with the airport saying passengers shouldn't travel to the airport without checking their flight status online first.

Elsewhere, airports and airlines advised customers to arrive earlier than normal for flights. Analysts said the outage was likely tied to a glitch in Microsoft software used globally.

Microsoft said users might be unable to access various Office 365 apps and services due to a "configuration change in a portion of our Azure-backed workloads".

Hong Kong International Airport said a Microsoft outage was affecting several airlines and it had switched to manual check-in, but flight operations had not been affected.

Singapore's Changi airport also said check-ins were being handled manually.

According to an alert sent by Crowdstrike to its clients and reviewed by Reuters, the company's "Falcon Sensor" software is causing Microsoft Windows to crash and display a blue screen, known informally as the "Blue Screen of Death".

The alert, sent at 0530 GMT on Friday, also shared a manual workaround to rectify the issue. A Crowdstrike spokesperson did not respond to emails or calls requesting comment.

The aviation sector is hit particularly hard due to its sensitivity to timings. Airlines rely on a closely coordinated schedule often run by air traffic control. Just one delay of a few minutes can throw off a flight schedule for take-offs and landings for an airport and airline for the rest of the day.

Airlines across the United States, Asia and Europe, including major carriers such as Ryanair, Delta and Air India, said they had either faced delays or disruption.

Several U.S. carriers including American Airlines, United Airlines and Delta Airlines issued ground stops for all their flights early on Friday due to communication problems, according to the U.S. Federal Aviation Administration.

In Europe, Schiphol airport, Berlin airport, London Gatwick, Edinburgh airport and others said they were impacted by the outage.

"We expect longer waiting times and some flight cancellations. Not all airports in Europe were impacted as the issue is linked with a specific OS, Microsoft Azure," said Agata Lyznik, a spokesperson for airports group ACI Europe.