Passenger traffic at Des Moines International Airport grew 8.6 percent in October over the same month last year, leaving the year-to-date gain at 6.6 percent. The largest carrier, American Airlines, gained 11.1 percent while Delta Air Lines saw a 2.4 percent jump. United Airlines gained 8.7 percent. With two months to go in the year, the airport had already served 2.3 million passengers. Based on the rolling 12-month average, it appears the airport will top last year’s all-time record of nearly 2.6 million passengers for the year, ending in the range of 2.7 million, if traffic patterns hold.