Flights in and out of Sydney, Melbourne and Canberra were delayed yesterday after two cables carrying radar and communications data were cut.
The cables, which link data services at all three airports, were cut during runway extension work at Canberra Airport, an Airservices Australia spokesman said.
Data including voice communications with aircraft and limited radar were still available to air traffic controllers via alternative links.
However, passengers at all three airports still suffered delays. Technicians were working on the problem and services were expected to return to normal today.