Propagated Delay vs Independent Delay Flight delay may be divided into two categories: Propagated delay Caused by inbound aircraft delay -function of routing 20-30% of total delay(Continental Airlines) >Independent delay Caused by other factors-not a function of routing 16
16 Propagated Delay vs. Independent Delay Flight delay may be divided into two categories: ➢ Propagated delay ▪ Caused by inbound aircraft delay – function of routing ▪ 20-30% of total delay (Continental Airlines) ➢ Independent delay ▪ Caused by other factors – not a function of routing
Definitions TDD PD IDD PDT ADT Slack Min Turn Time Planned turn Time PAT AAT PTT= PDT.-PAT PD lAD Slack= PTT-MTT AD PD= max( TAD- Slack 0) IDD=TDD -PD IAD.=TAD.-PD 17
17 Definitions i j Slack Min Turn Time PDT PAT ADT AAT PD IAD TAD j’ i’ i’’ PD IDD TDD j j i j j j i j i j i i j i j i j i j j i IAD TAD PD IDD TDD PD PD TAD Slack Slack PTT MTT PTT PDT PAT = − = − = − = − = − max( ,0) Planned Turn Time
Modeling Idea Delays propagate along aircraft routes Only limited slack can be added Appropriately located slack can prevent delay propagation Routing aircraft intelligently i better allocated slack Essentially add slack where advantageous, reducing slack where less needed 18
18 Modeling Idea Delays propagate along aircraft routes Only limited slack can be added Appropriately located slack can prevent delay propagation Routing aircraft intelligently ➔better allocated slack Essentially add slack where advantageous, reducing slack where less needed
lllustration of the dea f2 MTT f3f34 Original routing f1 f2 New routing 19
19 Illustration of the Idea f1 MTT f2 f3 f1’ f4 MTT Original routing f3’ New routing f1 MTT f2 f3 f1’ f4 MTT
Modeling Issues Difficult to use leg-based models to track the delay propagation One variable(string for each aircraft route between two maintenances(Barnhart, et al. 1998) Astring: a sequence of connected flights that begins and ends at maintenance stations Delay propagation for each route can be determined Need to determine delays for each feasible route Most of the feasible routes haven 't been realized yet PD and tAd are a function of routing PD and tAd for these routes cant be found in the historical data IAD is not a function of routing and can be calculated by tracking the route of each individual aircraft in the historical data
20 Modeling Issues Difficult to use leg-based models to track the delay propagation One variable (string) for each aircraft route between two maintenances (Barnhart, et al. 1998) ➢ A string: a sequence of connected flights that begins and ends at maintenance stations ➢ Delay propagation for each route can be determined Need to determine delays for each feasible route ➢ Most of the feasible routes haven’t been realized yet ▪ PD and TAD are a function of routing ▪ PD and TAD for these routes can’t be found in the historical data ➢ IAD is not a function of routing and can be calculated by tracking the route of each individual aircraft in the historical data