Airline delays dropped sharply in August at the country's 22 leading airports, the Federal Aviation Administration said, with one-third fewer delays reported over July's figures. The agency tabulates a delay when an aircraft is held up for at least 15 minutes because of weather or air traffic control reasons. Delays caused by mechanical or other problems involving an airline are not counted. According to the FAA, preliminary August figures showed a total of 27,298 flight delays, compared with 39,975 in July. FAA Administrator T. Allan McArtor attributed the decline to adjustments in the air traffic control system and airline scheduling changes that reduced the bunching of flights.