User manual

Last edited: July 14th, 2022

Cost platform

This article contains information about skailark’s cost platform. We begin with some important general notes before covering details on each cost item and conclude with the supporting information.

Forecasted (F) vs. Actual (A) values

Below the airline code and name you will see an indicator whether the data source is a skailark forecast (“F”) or whether it has been validated against published actual (quarterly/ annual) values (“A”). Some carriers only contain forecasted (“F”) values over time if the airline is not publishing financial values to any of our data sources.


Fuel consumption is modelled using skailark’s proprietary fuel consumption model. Fuel consumption is estimated per flight and by aircraft type and airline.

Fuel prices are estimated in a two-step process: First, average monthly Jet Fuel prices are adjusted for into-planing costs and taxes, where applicable. In a second step, this value is aggregated to a quarterly value and compared to the average quarterly jet fuel prices reported from airlines in their quarterly financial reports. If the latter is not available, the original price estimate is kept.

Allocation: Fuel consumption is calculated bottom-up, flight-by-flight. Therefore, no allocations are necessary.

Forecasting (until financial results published): Fuel consumption values are calculated flight-by-flight. Thus, as soon as the fleet information and satellite flight data is integrated into the model, all consumption values are calculated. Jet Fuel prices are estimated using the first approach described above.

Aircraft depreciation (owned and leased)

Aircraft depreciation is calculated bottom-up, by aircraft.

  • Aircraft purchase price is estimated using its published list price in the year of purchase in combination with skailark’s proprietary discount model of the specific order
  • Owned aircraft depreciation is calculated based on the aircraft purchase price and a depreciation over 25 years with a 10% residual. For aircraft older than 25 years, the residual value is distributed annually.
  • Leased aircraft depreciation is calculated along IFRS16 regulation over the expected lease duration. The aircraft market lease rate factor is split into a depreciation factor and a lease financing cost factor.

Allocation: Total depreciation costs are aggregated by operating carrier and fleet type and then distributed by BH to the respective flights.

Forecasting (until financial results published): Aircraft depreciation costs are calculated and forecasted based on skailark’s aircraft database. The models are calibrated with the key influencing factors and historic airline costs. There is no need to further calibrate with each airline’s quarterly financial data. Thus, as soon as the fleet information and satellite flight data is integrated into the model, all cost items are calculated. Thus, no special forecasting of aircraft depreciation data is needed/ happening.

Aircraft financing

Aircraft financing cost: To follow


MRO cost are calculated bottom-up by individual aircraft registration (tail number) and operating carrier. Costs are estimated separately along 4 main categories:

Engine & APU
  • Intervals between removals are dependent on engine maturity, aircraft flight patterns, engine derate and severity; the model is mimicking the engine exhaust gas temperature margin
  • Material and labour costs
  • Separately modelled for aircraft engine Limited Lifetime Parts (LLPs), shop visits, and for APU LLP and shop visits
Major airframe events
  • Heavy structural event intervals specific for each airframe
  • Material and labour cost estimates for individual shop visits
  • Key component overhaul/ replacement costs that are not covered in standard base maintenance are estimated separately.
  • Components include landing gear and thrust reversers
Line, base & burden
  • Line maintenance
  • Base maintenance
  • Maintenance burden
  • Line and base maintenance are estimated through a machine learning model, taking into account total fleet size, fleet FH to FC ratio, aircraft list price and aircraft age
  • The maintenance burden is calculated based on the total incurred MRO costs and a multiplication factor dependent on the type of carrier.

Data sources for MRO calculations are a skailark-proprietary database for intervals and cost items collected from various available data sources as well as from the team’s industry experience.

MRO cost accounting differs by airline. Some carriers depreciate major overhaul events for aircraft and engine components over time. Other carriers expense the costs as incurred. In the skailark product, the user can choose the preferred accounting method to ensure 100% comparability of the costs between the carriers. To achieve this, the major overhaul event costs for airframe and engines are calculated twice, once assuming depreciation of the events, and once assuming expensing as incurred. For the depreciation calculations, costs are depreciated over the interval between two major events or shop visits. The skailark cost platform allows the option to select the MRO cost accounting method as shown on the right.

Line and base maintenance costs are expensed as incurred either way.

Allocation: (Depreciated) costs are aggregated by fleet and month and than distributed to individual flights based on the flight hours of the fleet in the respective month. When marketing and operating carrier are not identical for a specific flight (e.g. wet leased aircraft), MRO costs are allocated to marketing carriers based on share of block hours of each marketing carrier.

Forecasting (until financial results published): MRO costs are purely calculated and forecasted based on skailark’s event-based internal data. The models are calibrated with the key influencing factors and historic airline costs. There is no need to further calibrate with each airline’s quarterly financial data. Thus, as soon as the fleet information and satellite flight data is integrated into the model, all cost items are calculated. Thus, no forecasting of MRO data is needed/ happening.


Both cabin crew and flight crew cost are calculated bottom-up, by FTE and BH.

  • Pilot salary and benefits per FTE:
  • Flight attendant salary and benefits per FTE:
  • Total pilot BHs and pilot cost/ BH:
  • Total flight attendant BHs and flight attendant cost/ BH:
  • Number of pilots and flight crew estimated per flight:



Handling cost: To follow


Airport aircraft and airport pax cost: To follow


ATC cost are differentiated between en-route cost terminal navigation charges and .

En-route cost are calculated for each flight based on three key input data:

  1. Distance flown through a specific airspace block
  2. Unit cost (per distance) for the specific airspace, which is based on
  3. Aircraft characteristics (mainly MTOW for most airspace blocks)

Terminal navigation charges (TNC) are based on two key input data:

  1. Unit cost at the specific airport
  2. Aircraft characteristics (e.g. MTOW)

Allocation: ATC costs are calculated for every flight individually, no allocations are necessary.

Sales/ distribution

Sales/ distribution cost description to follow


Catering cost description to follow

Other/ overhead

Other/ overhead cost is based on the delta between the skailark bottom-up cost calculations and the total operating costs reported by the respective carrier.

To allow for maximum comparability, the total operating costs exclude special items and costs related to non-aviation or 3rd-party revenue.

  • Special items contain non-recurring costs such as restructuring costs but also any COVID-19-related government support.
  • Costs related to non-aviation revenue contain costs related to revenue from non-aviation activities such as the operation of refineries, hotels, or other travel-related services.
  • Costs related to 3rd party revenue contain any costs related to 3rd-party MRO, ground handling or other aviation services provided to 3rd party airlines.

Please note: Given this exclusion of specific cost items, the total operating costs as well as CASM/ CASK reported by the carrier in their quarterly or annual reports might differ slightly compared to skailark’s output.

Allocation to cargo/ pax flight type: In case a carrier operates both cargo and passenger flights, these overhead costs are split between cargo and passenger flights, based on the share of the total bottom-up costs calculated for all cargo and passenger flights. Currently no costs are allocated to cargo transported in the aircraft belly.

Other/ overhead cost allocation to aircraft types [WB, NB, REG]: Costs are split to wide-/narrow-body and regional fleets based on the share of the total bottom-up costs calculated for these aircraft types. Total costs by aircraft types are then further distributed to individual flights based based on the ASK distribution.

Supporting information

Supporting information are the lines of data displayed below the cost data visualizations. In the following, we will explain the methodologies of some key information.

  • Density is calculated as ASK / ESK (or, ASM / ESM). ESK or ESM are defined by the maximum economy seats (or “exist limit”) as per the aircraft OEM’s type certificate data sheet multiplied by the respective distance flown.
  • CO2 emissions are calculated based on the bottom-up flight-based fuel consumption. 3.16kg of CO2 are emitted for each kg of fuel consumed, equivalent to ~21.1 lb of CO2 per gallon of fuel consumed. The latter is also impacted by the fuel density assumption, where we use 0.80kg/L.