Passenger traffic at Des Moines International Airport was down 5.4% in November compared with the same month last year. However, the year-to-date growth stands at 5.1%, considered a strong performance and in line with the average of the past few years. Kevin Foley, executive director and general manager, said the dip in November’s figure came in part because airlines added seats, boosting sales, last year about that time. He added that some of the Thanksgiving traffic this year spilled into December and will be reflected in that month’s data. The largest Des Moines carrier, American Airlines, gained 2.8% in passengers in November, and Delta gained 3.8%. The monthly total for United Airlines, the third-largest carrier here, was down 13.5%.