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CASK / RASK / PRASK airline unit economics
What it is
The core airline unit metrics. Cost per Available Seat Kilometre measures cost of supplying one seat one kilometre; Revenue per ASK measures what that seat earned; Passenger RASK strips out ancillary and cargo revenue
The RASK-CASK spread is the entire economics of an airline, and it is usually measured in single-digit paise
Impact on industries
- Scale, fleet commonality and high utilisation drive CASK down, which is why the largest carrier structurally outperforms on cost
- The spread is razor-thin, so small moves in fuel, currency or fares swing an airline between profit and loss within a quarter
- CASK is dominated by items outside management control - fuel at 35-40% of operating cost and dollar-denominated leases and maintenance
- Ancillary revenue lifts RASK above PRASK without adding seats, which is why baggage, seat selection and cargo now matter to the P&L