The websites of several German airports have been disrupted. "We are still troubleshooting," said a spokeswoman for Dortmund Airport on Thursday.

However, it is unlikely that the outage is due to a regular overload. "There is a strong suspicion that it could be a hacker attack." The websites of airports such as Düsseldorf, Hanover, Nuremberg and Erfurt-Weimar were also temporarily affected. "We suspect a DDoS attack was behind it," said a spokesperson for Nuremberg Airport. The website was down from around 08:10 until around 11:40.

In so-called DDoS attacks, a website receives so many requests within a short period of time that it collapses due to overload. There had already been such an incident at German airports, including Hamburg, at the end of January. Düsseldorf Airport explained that the website was currently unavailable. "The cause of the disruption has not yet been conclusively determined and the analysis by our IT partners is still ongoing."

Lufthansa experienced a failure of its IT systems on Wednesday - but not due to a hacker attack. An IT malfunction caused by a fiber optic cable being severed during railroad construction work in Frankfurt had temporarily paralyzed Lufthansa's flight operations at its most important hub.

(Report by Klaus Lauer; edited by Ralf Banser - If you have any questions, please contact our editorial team at berlin.newsroom@thomsonreuters.com (for politics and the economy) or frankfurt.newsroom@thomsonreuters.com (for companies and markets)).