The websites of seven German airports were hit by a suspected cyber attack overnight, the ADV airport association said, a day after a major IT failure at Lufthansa left thousands of passengers stranded.
Among the airports affected were Dusseldorf, Nuremberg and Dortmund, but websites for Germany's biggest airports in Frankfurt, Munich and Berlin were operating normally.
"Once again, airports fell victim to large-scale DDoS attacks," ADV chief executive Ralph Beisel said in a statement, adding the websites of seven airports were temporarily down.
A DDoS (denial-of-service) attack involves high volumes of internet traffic being directed to targeted servers in a relatively unsophisticated bid by so-called "hacktivists" to knock them offline.
"According to the information we have so far, other systems are not affected," said Beisel, adding the extent to which the situation will spread to other locations remains to be seen.