Airline capacity and traffic: ASK, RPK and load factor
Fleet, block hours, seat kilometres, passengers.
By Surojit Chakraverti, founder of L3VLUP and an investor running a long-short healthcare and technology equities strategy.
On this subject: airline capacity and traffic: ask, rpk and load factor.Updated 22 October 2026
What it does
The base of every airline forecast. Aircraft in service times the hours each flies a day times the days in the year gives block hours; times the block speed, kilometres flown; times the seats on board, available seat kilometres (ASK), the airline’s capacity. Kilometres over the average stage length give departures. Load factor is the share of that capacity sold: ASK times load factor is revenue passenger kilometres (RPK), and RPK over the stage length is passengers. Fuel, crew and maintenance follow block hours, airport charges follow departures and passengers, so this one schedule drives both sides of the income statement.
Where it lives
The same schedule in each model that carries it, with the rows to open. Open a model in the browser, go to the sheet, and click the lines.
- Assumptions, rows 17–33: Narrowbody: owned aircraft, FY0A, Narrowbody: leased aircraft, FY0A, Narrowbody: owned aircraft delivered, Narrowbody: leased aircraft added…
- Assumptions, row 36: Load factor, base case
- Fleet, rows 6–12: Narrowbody: owned aircraft, Narrowbody: leased aircraft, Narrowbody: aircraft in service, Narrowbody: block hours…
- Fleet, rows 15–21: Widebody: owned aircraft, Widebody: leased aircraft, Widebody: aircraft in service, Widebody: block hours…
- Fleet, rows 24–30: Aircraft in service, Leased share of the fleet, Block hours, Kilometres flown…
- Revenue, rows 6–12: Load factor, selected scenario, Narrowbody: RPK, Widebody: RPK, Revenue passenger kilometres (RPK)…
What a reviewer looks for
- Revenue forecast from a growth rate, so a fleet plan cannot move it.
- Departures and passengers that do not reconcile with kilometres and stage length.
- One utilisation figure for short-haul and long-haul aircraft.