[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 Tonne Kilometer (ATK) is defined as the output in units of cargo airlines.

ATK is actually a similar concept to the ASK in passenger airlines.