CASK = operating cost ÷ ASK
CASK ex-fuel = (operating cost − fuel cost) ÷ ASK
Example
An airline has 375 million in operating costs on 5 billion ASK.
CASK = 375,000,000 ÷ 5,000,000,000 = 0.075, or 7.5 cents per ASK.
Comparing CASK fairly
CASK depends heavily on the network. Longer average flights, denser seating and higher aircraft utilisation all lower CASK. When comparing airlines or routes, adjust for stage length, or compare CASK ex-fuel, before drawing conclusions.
How airlines use it
- Breaking CASK down by cost category (fuel, crew, maintenance, airport and handling, ownership) to see where costs move.
- Tracking fuel cost per block hour and per ASK.
- Comparing CASK with RASK by route to see which routes cover their costs.
CASK in Wireum Insights
Wireum Insights shows CASK/CASM broken down by cost category, fuel cost per block hour and per ASK, and ground-handling costs by station, alongside RASK and yield.
FAQ
Frequently asked questions.
Anything else? Ask us on a call or by email.
How is CASK calculated?
Divide total operating cost by available seat kilometres (ASK). It is usually expressed in cents per ASK. The miles equivalent is CASM.
What is CASK excluding fuel?
CASK with fuel costs removed. Because fuel prices swing widely, airlines and analysts use CASK ex-fuel to see how well the costs the airline controls are managed.
Why do longer flights have lower CASK?
Many costs occur per flight rather than per kilometre — airport and handling charges, take-off and landing, turnaround time. Spread over a longer flight, they add less per seat kilometre, so CASK falls as average stage length rises.
Wireum Insights
Wireum Insights is an airline operations and management dashboard that brings operational, commercial and passenger data — OTP, IROPS, AOG, load factor, RASK, CASK, NPS and more — into one configurable view, built on the airline's existing systems.