CLEARWATER — The number of passengers who use St. Petersburg-Clearwater International Airport increased by four percent in 2012, up to nearly 866,000. While domestic capacity rose three percent, most of that increase in passenger traffic is due to the 29 percent rise in international travel. Last year the airport started seasonal service to Toronto, Canada a month earlier than usual and added connections to Halifax, Nova Scotia. The airport's largest airline, Allegiant Air, served most of St. Petersburg-Clearwater's fliers in 2012: almost 744,000, a six percent increase from 2011. The number of routes to Gulfport-Biloxi International Airport rose to five times a week, resulting in a 62 percent jump of the number of people taking that flight.