American Airlines said Thursday it plans to suspend service to 15 small U.S. cities with low demand in October after the terms of federal aid requiring the flights expires, a move that would cut off scheduled flights to nine destinations in as many states.

The partial U.S. government shutdown will cost Delta Air Lines about $25 million in revenue this month as fewer government contractors and employees are traveling, the airline’s CEO Ed Bastian said Tuesday. The shutdown is the longest ever and has left some 800,000 government employees furloughed or working without pay.