PETERSBURG, ALASKA The state says a shutdown of the runway at Petersburg’s airport is planned for the middle of this September and should last between two to four weeks. The shutdown is part of a $20 million expansion of the safety area around the landing strip. It will require air travelers to ride a bus and ferry to Wrangell for Alaska Airlines flights out of that community. Petersburg City Council members Monday said they hoped to find out more about how and when that state project will happen.