It seems that MasterCard has your best interests in mind in Canada. In what is sure to be viewed as a test, the credit card company is offering an online booking bonus that ranks as the most lucrative in history. Residents of Canada who use a MasterCard to purchase at United’s Canada Web site (www.united.ca) get a chance to earn up to 35,000 bonus miles (with no limit on the number of times the bonus can be earned). Mileage Plus members using the magic credit card will earn a 10,000-mile bonus for a first-class booking or a 5,000-mile bonus for an economy-class booking between Canada and the United States or Mexico. Members who book online for destinations beyond the United States or Mexico earn 10,000 bonus miles for economy, 20,000 miles for business class and a 35,000-mile bonus for a first-class ticket purchase. The booking period runs through June 25; full payment must be made using a valid MasterCard; the offer is only valid for residents of Canada; qualifying flights are only on United, not code-share flights; the bonus may be combined with other online bonuses that United is now offering; there is no limit to the number of times the bonus can be earned and travel must be completed by April 30, 2002.