Passengers at Amsterdam's Schiphol airport faced long waits Wednesday due to a serious computer problem at air traffic control, causing scores of flights to be diverted, cancelled or delayed.

"We are not sure yet what the cause is or how long it will take to fix it," said spokesman Paul Weber. A reboot of computer systems at one of Europe's largest flight hubs failed to resolve the issue.

Delay times had mounted to more than 60 minutes, three hours after the problem was first discovered. Flights were being redirected to Germany's Munich airport and Rotterdam, he said.

Schiphol ranks among Europe's most congested airports with 58 million passengers in 2015.