The internet sites of several German airports were disrupted on Thursday after what may have been a hacker attack, German news agency dpa reported.
The disruptions did not appear to have an immediate impact on the country's air traffic, the agency said.
Nuremberg Airport in southern Germany reported that its online site was receiving so many requests that it collapsed.
The homepages of Duesseldorf and Dortmund airports in the west of the country were also unreachable, dpa reported.
In eastern Germany, the website of Erfurt-Weimar airport was shut down. The airport's internet provider was checking whether it was a hacker attack, dpa reported.
On Wednesday, Frankfurt airport had to temporarily divert all flights away from the country's busiest airport after a problem with airline Lufthansa's computer systems that was caused by construction works.