(Air Transport Industry)—a measure of the airline seating capacity available for sale. Each ASM is one seat flown one mile.

Available seat miles (ASMs) is a measure of an airline flight's passenger carrying capacity. It is equal to the number of seats onboard an aircraft multiplied by the distance flown in miles. For example, a 100-seat aircraft flying 100 miles would result in 10,000 ASMs. Seats that are not available for sale to revenue-paying passengers (e.g., seats reserved for crew rest, etc.) are excluded from this calculation. The amount of ASMs flown by an airline during a specified period equals the sum of ASMs flown on all flights during the period.

The aircraft miles flown in each inter-airport segment multiplied by the number of seats available for revenue passenger use on that segment. ( Small Air Carrier Statistics )