[Ref. The Global Airline Industry Edited By Peter Belobaba, Amedeo Odoni and Cynthia Barnhart © 2009 John Wiley & Sons, L td. ISBN: 978-0-470-74077-4]
Available Seat Kilometer (ASK) is the most common measure of airline output (capacity). It’s defined as one available seat flown 1 kilometer:
ASK = Num. of seat available x KM traveled
ASK is also known as Available Seat Mile (ASM), which is the most common measure of airline out. For example, if a flight can offer 200 seats and the route has 1000 km, then it generates 200 x 1000 = 200,000 ASK of airline output.
ASK is closely related to the unit cost, which is an important measure of cost efficiency, both over time and across airlines.
RPK is related to airline traffic – how much seats are sold as well as how much an airline can earn;
ASK is related to airline output – how much seats can be offered as well as the cost efficiency
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