NAV Canada attributed the outage to Zayo Group Holdings, Inc., one of its telecommunications services providers. Zayo a communications infrastructure platform, said the outage was caused by the disruption of two key fiber lines, partly because of a train derailment on Wednesday night. "We have rerouted a significant volume of traffic via other routes so that our customers can begin resuming normal operations," said Zayo, which provides bandwidth to customers including the tech and finance industries. Earlier on Thursday, the Greater Toronto Airports Authority (GTAA), which operates Toronto's Pearson, cited long lines at one of its terminals due to the outages, while Calgary International Airport said travelers may experience delays. Last week, a massive network outage at Rogers Communications Inc disrupted nearly every facet of life in Canada, including the call center service of the country's largest airline Air Canada.