Complaints began to emerge on Twitter earlier today, followed by reports that Amadeus, a computer system used by over 150 airlines, is down. Amadeus confirmed the news in a brief announcement from the company’s Group Communication Director, Stuart Brocklehurst, which reads:

Amadeus can confirm that some airlines are experiencing difficulties with our systems. We regret any delay and inconvenience caused and are fully investigating this issue.

Glitches appeared in the Amadeus system, which is used to issue tickets as well as check-in departing passengers, at around 3:30pm CET. After close to two hours, the problem appeared to be resolved, but the backlog created in those two hours could lead to a delay of flights that will last into tomorrow morning.

Finnair has reported dozens of delays which almost brought Finnish air traffic to a complete halt. Other airlines which have reportedly been affected by the Amadeus malfunction include British Airways, Lufthansa and Air Berlin.

Travel agency BCD tweeted that the outage was also affecting the ability to issue new tickets.

This is not the first time Amadeus has caused a significant delay in flights. In 2009 Amadeus outages led to Qantas Airlines having to manually check-in passengers, causing a delay of at least one hour for domestic and international flights.