Operation Yellow Ribbon () was commenced by Canada to handle the diversion of civilian airline flights in response to the September 11 attacks in 2001 on the United States. Canada's goal was to ensure that potentially destructive air traffic be removed from United States airspace as quickly as possible, and away from potential U.S. targets, and instead place these aircraft on the ground in Canada, at military and civilian airports primarily in the Canadian provinces of Nova Scotia, Newfoundland, and British Columbia. Yukon, New Brunswick, Alberta, Manitoba, Ontario, Northwest Territories, and Quebec also took in aircraft so that any malicious or destructive potential threats could be better contained and neutralized. None of the aircraft proved to be a threat, and Canada hosted thousands of passengers who were stranded until U.S. airspace was reopened. Canada commenced the operation after the U.S. Federal Aviation Administration (FAA), implementing Security Control of Air Traffic and Air Navigation Aids (SCATANA), grounded all aircraft across the United States, an unprecedented action. The FAA then worked with Transport Canada to reroute incoming international flights to airports in Canada. During the operation, departing flights—with the exception of police, military, and humanitarian flights—were cancelled, marking the first time that Canadian airspace had been shut down. In total, as a result of Operation Yellow Ribbon, between 225 and 240 aircraft were diverted to 17 different airports across the country. Deployment of emergency measures Immediately after the attacks on the World Trade Center (WTC), both Transport Canada and Nav Canada, the Canadian air navigation agency, activated their emergency measures. Transport Canada Transport Canada activated its situation centre (SitCen) in Ottawa at 09:21 EDT (13:21 UTC), 19 minutes after the second plane hit the WTC. The SitCen is Transport Canada's emergency operations center (EOC), originally constructed to deal with earthquakes along the British Columbia Coast. It had been used several times prior to September 11, 2001, including the January 1998 North American ice storm and after Swissair Flight 111 crashed off the coast from Peggy's Cove, Nova Scotia, on September 2, 1998. As personnel staffed the SitCen, key organizations such as Nav Canada, the Department of National Defence, the Royal Canadian Mounted Police (RCMP), Canadian Security Intelligence Service (CSIS), Citizenship and Immigration Canada (CIC), and Canada Customs and Revenue Agency (CCRA) were also involved in SitCen operations. One of the tasks of the SitCen was to maintain contact with other members of