The organization responsible for air traffic control in Canadian airspace says a severe thunderstorm in Ottawa was to blame for an outage affecting its automated flight planning system.

Nav Canada president Neil R. Wilson said in a statement Saturday evening that the water flooded one of its facilities shortly after midnight, affecting the network that handles flight plans and requiring staff to evacuate to a nearby facility where back-up systems are located.

The system was restored at 3:30 p.m. ET , but residual delays are possible until the backlogs clear, the statement said.

"Safety has not been compromised," Wilson added.

Earlier Saturday, the air navigation service said it was "experiencing a problem with the flight plan system" and that delays could be expected, particularly for international flights.

"Air traffic controllers are able to see and talk to airplanes," said Ron Singer, spokesperson for Nav Canada, in a text to CBC Toronto.

Flight plans that would normally be automatically fed into the service's system needed to be added manually until the problem was fixed, Singer explained.

He added that the domestic system was functioning properly, and the outage was confined to the "North Atlantic airspace," impacting primarily flights coming to Canada from Europe.

A spokesperson for the Greater Toronto Airports Authority, which oversees Pearson airport, said operations are running smoothly at Canada's biggest airport.

We are experiencing a problem with the flight plan system and are actively working to restore service. 1/2 —@navcanada