EDINBURGH/LONDON/SEOUL, July 19 (Reuters) - Air

passengers around the world faced delays, cancellations and

problems checking in as airports and airlines were caught up in

a massive IT outage that also affected industries ranging from

banks to media companies.

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 ( MSFT ) software used globally.

Microsoft ( MSFT ) 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 ( MSFT ) 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 ( AAL ),

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.

Some airlines said they were already back online, with

Spanish carrier Iberia saying it had managed to avoid flight

cancellations.

"From 9:25 a.m. onwards the electronic check-in counters and

online check-ins were reactivated. There have been some delays,"

a spokesperson said.