There are nine airports in the Greater Toronto Area. Pearson, City Centre and Hamilton have scheduled passenger service; however, the vast majority of passenger traffic goes through Toronto's Pearson International Airport, which is Canada's busiest airport and the country's major hub. Hamilton handles some discount flights and charters and acts as an alternate to Pearson. City Centre (Island Airport) is used for civil aviation, air ambulance traffic and regional scheduled airlines. Buttonville formerly had scheduled passenger service from Ottawa operated by Bearskin Airlines, but it has been discontinued. Hamilton is popular with charters and discount airlines who want to avoid fees at Pearson, which is among the world's most expensive airports. YTO is a multiple airport code that works for Pearson, City Centre, and Buttonville.