Here are a few terms and definitions:
- local % is the percent of local passengers on that segment (not connecting)
- SLA Yield is Stage Length adjusted yield. Average onboard fare (seg fare)/mileage stage length adjusted to normalize for distance based on the user's Target Stage Length input.
- PRASM is unit revenue, specifically segment passenger revenue per ASM
- SLA PRASM is the above but stage length adjusted
- % Free is the percent of total onboard pax "free tickets". These are frequent flyer award redemptions
- % Lcl Free is the percent of local passenger "free tickets".
- Lcl Fare= Avg local fare, the average fare paid by the local passengers only.
- Seg fare= Avg onboard fare. Local pax revenue + connecting passenger revenue (mileage prorated from connecting fares allocated to that segment) / Total pax onboard the flight. It is the average prorated fare for the segment based on the mileage ratio of that segment over the total route miles, calculated by the square-root-of-miles method.
- Sys Fare= also known as 'beyond fare', is the average fare paid for all passengers for which this is a segment of their full trip (Avg upline/downline fare from connecting passengers).
- Yield = Revenue divided by RPM (revenue passenger miles) using the total pax per day where:
Revenue = (total pax per day) * Seg Fare
RPM = (total pax per day) * mileage of route
Please note: Free pax won't have an effect on PRASM since revenue and ASMs remain unchanged regardless if they are included or not. It does however affect avg fare and yield. The average fares used in this report use the total number of onboard pax on this route, regardless of they were paid or free. So Avg fare = (Total Passenger Revenue)/(Total pax including “free” revenue pax).
The report uses both US DOT O&D (DB1B) and T-100 data to calculate PRASM. PRASM = Yield * Load Factor = (Seg Fare / Miles) * Load Factor and is updated on a quarterly basis with 3-month lag. Please check the U.S. DOT O&D data release date for the next Airline Performance data load.
Load Factor is derived from T-100 data.
Moving on to DB1B fare data, the Segment Fares is the average fare that sticks with the flight segment. Local passengers only fly on one segment, so the Local Fares contribute 100%. But for the connecting passengers, the System Fares are allocated among all the different flight segments on which the passenger flies. So unfortunately there’s no math you can do on the sheet here to replicate the Segment Fare—it’s all done behind the scenes with fare proration.
I’ll walk you through our SLA process so that you can understand how the SLA values are calculated.
First off, we actually calculate and use three different average stage length values for each route:
- Departure weighted - shown as the Total Average Miles in the Airline Performance report
- Passenger weighted average miles – used to calculate the Total Average Yield and Total SLA Average Yield
- Seat weighted average miles – used to calculate the Total Average PRASM and Total SLA Average PRASM
We calculate a “SLA Factor” for each route. The formula for the Factor = Sq Rt(Target mileage) / Sq Rt(Route Actual mileage)
We then use this Factor to stage length adjust both the Yield and PRASM values (e.g., SLA RASM = Seg PRASM / SLA Factor)
Airlines vary their SLA calculations by region/entity but at a high level, here is a walk-through of some of the basics:
Stage Length Adjustment Formula |
Y = mX + b |
Y = Cost per E-Seat (Divide by Stage Length [X] to get cost per seat mile) |
X = Stage Length |
m = Incremental cost per mile (slope) |
b = Fixed cost per departure (intercept) |
To apply this to a unit cost/revenue metric, you would do the following:
Formula |
SL Adjuster 1 = (((Target SL * Slope) + Intercept)) / Target SL) / (((Actual SL * Slope) + Intercept)) / Actual SL) |
For example, heres what a SLA calculation would look like if the Slope = 0.0562, intercept = 49.348 and a target SL of 1000.
Formula Example | ||
Airline XX | Industry | |
Nominal PRASM | $0.0898 | $0.0899 |
Stage Length | 1,129 | 1,030 |
Slope for Region | 0.0562 | 0.0562 |
Intercept for Region | 49.348 | 49.348 |
Target SL for Region | 1,000 | 1,000 |
SLA Adjustor | 1.056 | 1.014 |
SLA PRASM | $0.0949 | $0.0911 |
Hopefully this gives you the information you were needing to better understand how our values are being calculated in the Airline Performance report.
Does the O&D data include non-revenue passengers:
https://helpdesk.cirium.com/hc/en-us/articles/360024567552-Does-O-D-data-include-Non-Rev-passengers
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