AIRLINES

U.S. Probing Commission Practice: The Department of Justice is investigating a widespread practice among big airlines of giving fatter commissions to travel agents who send more passengers their way, industry sources said. The practice is especially common at cities with hub airports, which act as connecting points for flights to and from other cities. But small, upstart airlines complain that the practice makes breaking into a market more difficult and that passengers steered to a bigger airline frequently pay more. Investigators so far have focused on Salt Lake City, where Delta Air Lines operates a hub and competes with low-fare, no-frills Morris Air. Delta last year handled nearly 85% of the passengers traveling through Salt Lake City International Airport.