A hub of activity┬áThough at first glance airports appear to have their own captive markets, behind the scenes there is a great deal of competitive activity, as Alan Swaby learns. At Montr├®al-Trudeau International Airport, visitors from the United States are a pretty pampered lot. In order to give them a last taste of Canadian relaxation before being reabsorbed into the hurly-burly of home life, American visitors are allowed to clear customs and immigration back into the US before theyÔÇÖve even finished their trip to Quebec.