E-ROAR: Enhanced Robust Operational Aircraft Routing

Bringing Airline Planning And Operations Closer Together

Enhanced Robust Operational Aircraft Routing (E-ROAR) is a highly advanced planning tool from Sabre Airline Solutions (the “enhanced” element builds on, and goes beyond, the already-substantial success of ROAR). E-ROAR, then, serves as an even more powerful, capable and flexible post-process to the Sabre AirVision Fleet Manager, helping bridge the gap between airline planning and operations.

In the modern, ultra-competitive world of commercial air transportation, planning tools are critical, as they integrate combinations of factors to produce optimum paths, or a selection of optimum choices depending on airline objectives.

As conventionally understood and applied by carriers globally, airline planning is a fundamental set of procedures comprising flight scheduling, fares management, revenue management and distribution (collectively, sometimes referred to as the marketing/planning process).

That first element, flight scheduling, actually involves a longer-term set of procedures. Flight scheduling, therefore, is quite properly and appropriately considered strategic, on the basis that macro-demand forecasts are created five years out to formulate future schedules.

Meanwhile, revenue management (the third element of airline planning as listed above) is based on current schedules. Fare management and revenue management are both considered “tactical” processes that look ahead 12 months.

These are essentially disparate issues (in that flight scheduling is longer-term, whereas fares management and revenue management derive their figures from more current or even real-time factors).

How can these critical issues be reconciled, and even more pointedly optimized, under the common overall umbrella of flight planning to any reasonable degree of efficiency?

Reduced Planning-Cycle Time

Table 1 describes 11 scenarios. For example, scenario XX_32A has 10 aircraft, seven-day window and 280 flights with one maintenance station (three-day maintenance requirement). Scenario YY_734 has 18 aircraft, seven-day window and 547 flights with nine maintenance stations (three-day maintenance requirement). Table 2 summarizes the computational results achieved when using E-ROAR. The three-step approach can remove almost all infeasible maintenance strings. This, thereby, better facilitates downstream processes while representing tremendous value to airlines through tangible, substantial reduction in the planning-cycle time.

E-ROAR To The Rescue

These issues are precisely what E-ROAR, or Enhanced Robust Operational Aircraft Routing, has been developed to address and solve through applicable mathematical formulas, with a certain flexibility and broad capability that can benefit airlines of any size and operating philosophy.

To view all the elements of flight planning in an appropriate outlook requires broader perspective, and inclusion of further analytic parameters.

Very specifically, E-ROAR has been developed to more readily and efficiently integrate airline fleeting and build aircraft routings with operational requirements, including periodic maintenance (many requirements with a mandatory three-day frequency), avoiding sequential tight turns (operational robustness) and rigidly enforced crew rules.

E-ROAR thereby better facilitates downstream processes encompassing maintenance planning, crew planning and daily operations, while representing tremendous value to airlines through tangible, substantial reduction in the planning cycle time.

Logical Concepts Underpinning E-ROAR Applications

E-ROAR’s development is the product of a natural progression in planning tools. Its antecedent, ROAR (Robust Operational Aircraft Routing),moved the planning needle in commercial aviation. The next step forward is represented in E-ROAR, which has been built on established logical concepts such as the the Fleet Manager model that have proven value in the broader industry.

Fleet Manager achieves the demand-to-capacity match by determining which fleet types map to which flight legs.

Effectively, Fleet Manager is used with a weekly schedule to accomplish the fleet assignment, and if anomalies occur, airline planners sometimes add a day on each end of the sequence to bridge the schedule (which, for example, commonly happens when there is a change in season).

Assignments are made by fleet type, and airline planners already know the count of aircraft by fleet type that is required to map to the various flight legs.

Bear in mind, however, that Fleet Manager is simply a planning tool, and while planners know what aircraft type maps to any particular flight leg, they likely have no idea about the tail number of a specific aircraft (tail-number assignment is handled down line in airline operations).

E-ROAR is a post-process to Fleet Manager that is intended to ensure that avoiding tight connections, crew rules and maintenance requirements are not only considered but incorporated.

To illustrate, in E-ROAR, the airline planner knows that Leg A connects to Leg B and has a specific fleet-type assignment. Basically, E-ROAR ensures that the “flight strings” are meaningful for crew planning, maintenance planning and airline operations, because the flight strings are fashioned (through E-ROAR) to be crew-constraint-friendly and maintenance-constraint-friendly

And that facet serves to minimize those departments’ necessity to rework the flight strings in creating a flyable schedule.

Herein is a huge value proposition, in that E-ROAR essentially serves to smooth the process to the creation of a flyable schedule, thus making it possible for crew planning, maintenance planning and airline operations to devote more of their extremely valuable time and energy to addressing and solving other critical issues.

Three-step Approach

The solution approach consists of three steps. The first step is to use the Leg Connection Model (LCM) to find an initial solution. The second step is to use the swap heuristic to improve the initial solution. The last step is to use the Maintenance String Model (MSM) to further improve the solution from the swap heuristic. After these three steps, almost all infeasible maintenance strings can be resolved.

The Figures Behind The Analysis

A mixed aggregation of heuristic and optimization approaches were designed to handle the exponential growth in flight-string variables as input. Such an approach serves to balance solution quality and performance, and is preferable in comparison to the branch-and-price optimizer.

The final schedule from Fleet Manager, incorporating analysis derived from the E-ROAR post-process, then goes to airline operations.

In turn, airline operations makes tail-number assignments (in assigning tail numbers, airline operations can apply the Aircraft Routing Model, a part of Sabre AirCentre Movement Manager).

To properly evaluate both the efficiency and the cost savings gained from the application of E-ROAR as a post-process to Fleet Manager, a Key Performance Indicator (KPI) will be the number or percentage of tail assignments that can be made automatically.

The end result is a flyable schedule, and enormous measures of efficiency gained over previously available planning/operations integration techniques.

Swap Heuristic

Shown is the basic idea of swap heuristic and how the connection swap fixes the infeasible maintenance strings. Each small circle represents a flight, and the arrowed segment represents the connection between flights. It is assumed that each aircraft must visit the maintenance station no more than three days. The first flight string is illegal since it will be away from the maintenance station for four days. The swap heuristic will find a string, which is away from the maintenance station for two days, and swap these two strings in the middle. After the swap, both strings are legal and away from the maintenance station for three days.

A Few Specific Examples

Results can be graphically illustrated for various scenarios. Revealing what it’s pretty easy to see amounts to significantly enhanced efficiency.

Salient examples include a scenario involving:

  • 10 aircraft, a seven-day window and 280 flights, with one maintenance station (and a standard three-day maintenance requirement).
  • 15 aircraft, a seven-day window and 224 flights, but with nine maintenance stations (and, again, a three-day maintenance requirement).
  • 18 aircraft, a seven-day window and 547 flights (with nine maintenance stations and a three-day maintenance requirement).
  • 68 aircraft, a seven-day window and 1,531 flights, nine maintenance stations and a threeday maintenance requirement.
  • 121 aircraft, a seven-day window, 2,869 flights and nine maintenance stations (again, with the standard three-day maintenance requirement).

Substantiating the validity of all scenarios illustrated is a computational summary of “illegal flight strings,” which decreases dramatically upon timely and appropriate application of E-ROAR as a post-process to Fleet Manager. In fact, among the scenarios just cited, none (after application of E-ROAR) resulted in an illegal flight string.

Analyzing objectively, an occasional illegal flight string (which must then be manually reworked to assure that the string is made legal) still crops up regardless of E-ROAR application, but in far rarer circumstances.

So the efficiencies gained through E-ROAR, and the resultant cost savings, could very well prove to be extremely significant factors at an airline’s bottom line, which, of course, is the objective of every tool developed in the industry.

Based on thorough and continually accumulating analysis, E-ROAR stands as a beacon of potential strategic utility where it really counts: in cost savings that can be dramatically and convincingly demonstrated in real-life scenarios.

A Bright Future Of Efficiency

E-ROAR represents a timely development in flight planning, significantly improving on alreadylaudable ROAR results and offering airlines globally an even more powerful and usable tool to increase efficiency and reduce costs.

It’s another in the arsenal of effective planning tools, furthering the opportunity of every carrier to effect change for the better, as well as achieve positive results far into the future.