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# What Is CASK in Airline Economics?
- URL: https://www.acmiworld.com/what-is-cask-in-aviation/
- Published: 2026-09-14T16:35:44.000Z
- Updated: 2026-09-14T16:35:44.000Z
- Description: CASK defined for aviation professionals, with its operational or commercial use, document context and related terminology.
- Author: ACMI World
- Tags: Aviation Glossary, Airline Economics & Scheduling, #Import 2026-09-14 15:41

## Definition and Operating Context

Cost per Available Seat Kilometre, or CASK, divides an airline's operating cost by available seat kilometres.

Aviation Glossary

**Term:** CASK

**Category:** Airline Economics & Scheduling

## How Airlines Use the Metric

CASK is used to describe capacity, traffic, cost, revenue, schedule performance or asset productivity. It is most useful when the calculation basis is consistent across the periods, airlines or fleets being compared.

## What the Number Can Show

It is a core unit-cost metric, but comparisons need care because stage length, fleet mix, accounting policy and whether fuel is included can change the result materially.

## Comparison Limits

Airline metrics can be distorted by stage length, fleet mix, geography, accounting treatment, seasonality and business model. A single ratio should therefore be read with the operating context and the underlying numerator and denominator.

## Related Aviation Topics

Related ACMI World coverage includes [ACMI lease pricing](https://www.acmiworld.com/acmi-lease-pricing-explained-what-airlines-actually-pay-for-capacity/), [seasonal ACMI demand](https://www.acmiworld.com/seasonal-demand-and-acmi-leasing/), [the 2026 capacity environment](https://www.acmiworld.com/why-airlines-are-turning-to-acmi-in-2026-gtf-groundings-delivery-delays-and-the-capacity-crunch/), [aircraft lease rates by model](https://www.acmiworld.com/aircraft-lease-rates-by-model-in-2026/) and [leading ACMI operators](https://www.acmiworld.com/top-20-acmi-operators-in-the-world-2026-rankings/).

It is a core unit-cost metric, but comparisons need care because stage length, fleet mix, accounting policy and whether fuel is included can change the result materially.

Frequently Asked Questions

## CASK FAQ

What does CASK mean in aviation?

Cost per Available Seat Kilometre, or CASK, divides an airline's operating cost by available seat kilometres.

Why does CASK matter?

It is a core unit-cost metric, but comparisons need care because stage length, fleet mix, accounting policy and whether fuel is included can change the result materially.

Where would an aviation professional encounter CASK?

It is commonly encountered in airline economics & scheduling documents, procedures, calculations or operating discussions where the underlying technical or commercial issue is relevant.

Can the metric be compared directly between airlines?

Only when the calculation basis and operating context are sufficiently comparable. Stage length, fleet mix, geography and accounting policy can materially change the result.