Why RESM ^™ (Revenue per Enilria Seat Miles)? 

RASM (Revenue per Available Seat Miles) are regularly used for analysis of route and network performance in the airline industry, but RASM has several inherent weaknesses. 

* Differences in mileage make it incomparable when different routes are compared. 

* Network route evolution over time make it incomparable at a network level because average stage length changes.  

* RASM treats seats as a constant as well, but the number of seats on an airplane can vary wildly, and that is becoming a bigger problem lately with expansion of premium seating areas.  

* An airline can boost RASM by simply reducing seats, but the RASM boost is a performance mirage since revenue is unchanged, but divided over fewer seats.  

* To fix both items, a more constant and reliable value needs to be used to make comparisons more valid, even within the same airline.  

 

Fixing the Distance Problem 

Fixing the difference in distance has largely been solved by adopting a mathematical root based formula to make distances correlate more closely to cost. Airline costs do not increase directly with distance.

* Airport related costs continue to grow faster than most other costs and Cost Per Enplanement (CPE) at some airports can now reach $50. While RASM is intended to track revenue and not cost, it needs to be aligned more with the airline cost distance curve to allow RASM to be more useful for analysis without the context of other factors like stage length aka distance. 

* While infrequently discussed, the cost to get an airplane to cruising altitude is a disproportionately large % of fuel and time related costs. A takeoff and landing typically adds about 37 minutes to the time of a point to point flight, for zero additional miles traveled. Even a flight from Chicago MDW to Chicago ORD would likely require about 40 minutes of block time. On a 1 hour flight, 30% of the fuel burned is in the 10-12 minutes from takeoff roll to cuising altitude despite it being only being less than 20% of the flight time. On longer flights with more payload and fuel the amount burned initially is even higher. There are also costs specific to landing such as landing gear replacement that make a root based revenue formula track more closely to cost.  

* RESM (TM) uses a root of the distance approach like other "Stage Adjusted RASM" metrics. 

 

Fixing the Seating Density Problem 

The problem is that a CRJ-550 has 50 seats and a CRJ-700 has 70 seats. They are essentially the same aircraft. We also see this with JetBlue Mint and other seating configurations where the aircraft has far fewer seats than it is able to accomodate. This "gooses" RASM by dividing revenue over fewer seats...AND it has a double impact because average fare on a low density aircraft is typically higher. These effects make removing seats automatically look great for RASM. To some extent it is just a mirage.

* To fix this we have researched the maximum FAA approved seating configuration for the aircraft. This is typically driven by number of emergency exits and other factors. Typically manufacturers want to offer a very dense configuration for any plane, even if it does not sell. This number is a much more reliable measure of how much the aircraft can carry and is also relevant to the cost of the aircraft both in terms of purchase cost (ownership burden), fuel burn, and mechanical/maintenance needs. One could also argue that many overhead costs also should be tied to departures rather than seats. For this reason RESM ^™ is connected to maximum seats rather than actual.  Thanks to Patron RWA380 for contributing assistance on creating the maximum seating charts.    

* RESM ^™ does use a weighted blend of the maximum configuration and the actual configuration to allow for some cost savings tied to fewer seats like flight attendant staffing, meals loaded, and gate staffing. Generally, however, costs don't change that much when seats are removed and the weighting reflects that.

 

Where Will RESM ^™ Be Used? 

Starting in 2026 RESM ^™ will start to appear on some reports on the Enilria.com site.