preliminary evaluation of flight delay propagation ... - ATM Seminar

AbstractAirline flight schedules are particularly sensitive toindividual flight delays because of the manner inwhich operating resources are linked together.Among the connective resources affected by delayedflight operations are crews, aircraft. passengers andgate space. Because of this branching connectivitythe delay of one flights tends to propagate rapidlydown line to many others. In order to evaluate aninitial flight delay on an airline operating schedulethis paper proposes the concept of a Delay Multiplier(DM).Using American Airlines crew and aircraftconnectivity through an actual airline operatingschedule the DM demonstrates the value of delay (ordelay reduction) on the operating schedule as awhole. The relationship between the duration ofinitial delay, the time of day of the delayoccurrences and airline schedule connectivity areused to calculate the value of the DM.Specifically, this process was developed to evaluatechanges in the FAA's Air Traffic ManagementGround Delay Program procedures.Background1. The ProblemWhen the flight arrival demand exceeds an airport'sacceptance capacity, it is the job of the FAA's AirTraffic Control System Command Center(ATCSCC) to control demand. This is often donethrough the use of a technique called the GroundDelay Program (GDP). Under this programATCSCC issues Controlled Times of Arrival (CTAs)to flights still on the ground but destined to arrive atthe constrained airport to ensure the airport capacityis not exceeded. GDP can produce delays forindividual flights ranging from a few minutes toseveral hours. These delays are of concern to anyuser, but are most disruptive to airline operatorswhose schedules are made up of tightly connectedoperating resources (i.e. aircraft and crews).Intuitively, large delays early in the operating dayare most disruptive, while short delays (or delays latein the day) have little or no propagation through theschedule.To better understand the total effect of airline flightdelays produced by ATCSCC GDPs, AmericanAirlines and Oak Ridge National Laboratorycollaborated on a joint study to see if a numerical"delay multiplier" (DM) could be derived that wasbased on the length of the initial delay and the timeof day it occurred.This was not an attempt to predict the actualdownline effect any given flight delay wouldproduce, but rather to develop a "generic" total valueof both the initial delay and its continuingconsequences on the airline schedule. This totalvalue could then be used in the evaluation of changesin GDP procedures.It seemed obvious to those that operate airlineschedules that reducing a 60 minute delay to 30minutes is much more valuable than reducing a 30minute delay to zero. The question is: How does thevalue of initial delay reduction vary based on boththe length of the initial delay and the time of day atwhich it occurs?It is important to note that, for an airline, the "value"of delay is not just its effect on an individualairframe but its effect on the operating schedule. Itis this schedule that is the primary product offeredto the traveling public. Passengers do not go out tothe airport to fly on a specific airplane or with aspecific crew. They go to catch the two o'clockflight to Chicago which is promised in the airline'spublished schedule. A significant part of the airline'sday-to-day operational effort is expended in theattempt to keep that promise.2. The Concept of Delay Multiplier (DM)To establish the value of the DM we decided toanalyze the conductivity of crew sequences andaircraft sequences though the American Airlinesflight schedule. While these are the obvious andprimary assets needed to operate flights, there areother resources that are affected by delayed flightoperations that were not considered due to theircomplexity. Most notably, the affect of delayedoperations on passengers, cargo and gate space werenot considered. Each of these can induce delays inother flights. Therefore we believe our calculatedDMs based on crew and aircraft only to be highlyconservative.The concept of Delay Multiplier can be consideredas that value, which when multiplied by the initialdelay, would yield all of the potential downline2