It may take several more days before operations return to normal, and it remains unclear when the problems will be fully resolved.
An airport representative warned travelers to expect delays, cancellations, and long waits in the coming days amid ongoing emergency efforts to restore systems.
Passengers are urged to check their flight status directly with their airlines, complete online check-in before arriving at the airport, and use the self-service kiosks available through 19 carriers in the terminal.
According to Spiegel, other major German airports were not affected by the cyberattack.
The disruption began on Sept. 19, when airports across Europe reported severe operational problems after a cyberattack on Collins Aerospace, the U.S. software provider behind widely used check-in and boarding systems.
The EU Agency for Cybersecurity (ENISA) confirmed that the outage was caused by a “third-party” attack, which led to long lines and boarding delays at airports in Brussels, London, Berlin, and other cities.
Meanwhile, Copenhagen and Oslo airports have resumed operations after being temporarily shut down due to drones in their airspace.