5/25/2015 Operations Research Group Continental Airlines Bridging Schedule Changes When Bookings Exist Judy Pastor Continental Airlines AGIFORS YM Berlin

5/25/2015 Operations Research Group Continental Airlines On September 1, 2001 Airline industry changed dramatically Continental reduced schedule by 20% But bookings existed on full schedule for the next 330 days Situation magnified an existing problem

5/25/2015 Operations Research Group Continental Airlines CRSs and Schedule Change Continental’s CRS Reaccom process –Input is flight (old schedule) to flight (new schedule) mapping for a future date range –All passengers from flight in old schedule are moved to specific flight in new schedule No attention given to connecting segments AU levels for new flights are not respected Human intervention needed to correct

5/25/2015 Operations Research Group Continental Airlines Result of Current Process Costly in terms of –Customer Satisfaction Self-imposed misconnections for connecting pax Confusion at airport –Recovery “Hot” flights  DB Costs Reaccom at airports –Revenue opportunity LY pax moved to flights with HY opportunity

5/25/2015 Operations Research Group Continental Airlines Schedule Change Reaccom OR group saw opportunity to combine rich information contained in PNR Data Warehouse and Mathematical Programming Solution –Build new flight network and flow passengers from existing schedule onto it –Large problem that looked intractable at first –Analysis led to ways to reduce it

5/25/2015 Operations Research Group Continental Airlines Multi-Step Process Current algorithm focuses on one day of reaccom but recognizes prior and subsequent days –Due to itineraries that span days –So that reaccom can be done in one flight/day markets

5/25/2015 Operations Research Group Continental Airlines Schedule Match Get proposed schedule from Schedule Administration Retrieve current schedule For each date of interest, match proposed schedule to current Each flight in new schedule is either a Match or a Change

5/25/2015 Operations Research Group Continental Airlines Types of Flight Changes No Match –Caused by a change in frequency –Flight in old schedule has no match in new Retime –Old flight matches in new schedule but with timing change Into Hub – arrival time > 10 min later Out of Hub – departure time > 10 minutes earlier Any time change more than 30 minutes Match with Equipment Downgauge –If current bookings > new capacity

5/25/2015 Operations Research Group Continental Airlines Schedule Match Example OD: RDUIAH DeptDate: DOW: 7 Old Schedule Num Flights: 3 FltNum 151 Dept 635 Arrl 829 Bkd 34 AU 110 CAP 104 Status: OK FltNum 1751 Dept 1453 Arrl 1650 Bkd 77 AU 110 CAP 104 Status: No Match FltNum 551 Dept 1740 Arrl 1935 Bkd 36 AU 135 CAP 124 Status: OK New Schedule Num Flights: 2 FltNum 151 Dept 635 Arrl CAP 104 Status: OK FltNum 551 Dept 1740 Arrl CAP 124 Status: OK Old Total Cap: 332 New Total Cap: 228 Bkd: 147 Re-Timed: 0 No Match: 77 Downgauge: 0

5/25/2015 Operations Research Group Continental Airlines Effected PNRS Next step is to retrieve PNRs for flights that are classified as a Change –Get all active legs in PNR for the focus date, the day before and the day after Create new schedule with recomputed current booked, capacity and AU –Matched flights get booked from old schedule minus any connecting legs from PNRs of changed flights –Unmatched flights will have current booked of zero

5/25/2015 Operations Research Group Continental Airlines New OD Paths Enumerate feasible O and D paths for new schedule for PNRS from changed flights –Non stops –One stops (limit to total trip time < nonstop + 4 hours if nonstop exists) –Two stops (if less than 6 paths) –Three stops (if nothing yet) –Alternate stations can be penalty

5/25/2015 Operations Research Group Continental Airlines Alternate Paths for RDUGYE RDUIAH IAHPTY PTYGYE RDUEWR EWRPTY PTYGYE RDUEWR EWRPTY PTYGYE RDUEWR EWRPTY PTYGYE RDUEWR EWRPTY PTYGYE RDUEWR EWRPTY PTYGYE RDUIAH IAHPTY PTYGYE RDUIAH IAHPTY PTYGYE RDUIAH IAHUIO UIOGYE RDUIAH IAHPTY PTYGYE RDUEWR EWRPTY PTYGYE RDUEWR EWRPTY PTYGYE RDUEWR EWRPTY PTYGYE

5/25/2015 Operations Research Group Continental Airlines Demand Aggregate demand by Path O and D and class of service Flow aggregated demands on new schedule network via the enumerated paths to minimize penalties –Change from original departure, arrival, trip time –Number of flights in itinerary –Multiplier for class of service (more penalty for YH) –Use of alternate stations for origin or destination

5/25/2015 Operations Research Group Continental Airlines Flight Capacity Constraints Capacity constraints on flights in new schedule –RHS for matched flights = new cap – recomputed current booked –RHS for changed flights = new cap Solve LP Solution will flow old path O and Ds by class of service on new schedule

5/25/2015 Operations Research Group Continental Airlines Solution Example OLD FLT 1751 RDUIAH Dept 1453 Arrl NO MATCH IN NEW SCHEDULE Path RDUGYE NumPax 76 COS B #Flts 3 PathDate Dept 1453 Arrl 2359 Penalty 43.4 FLT 244 ddate od RDUEWR dept 1400 arrl 1529 FLT 887 ddate od EWRPTY dept 1750 arrl 2200 FLT 887 ddate od PTYGYE dept 2250 arrl 2445

5/25/2015 Operations Research Group Continental Airlines Assign Existing PNRs Assign PNRs to new paths via bin packing algorithm –blocks of space assigned by O and D –individual PNRs must now fit into blocks as closely as possible –may need to amend “optimal” solution to fit PNRs exactly

5/25/2015 Operations Research Group Continental Airlines PNR Assignment OLD FLT 1751 RDUIAH Dept 1453 Arrl NO MATCH IN NEW SCHEDULE Path RDUGYE NumPax 76 COS B #Flts 3 PathDate Dept 1453 Arrl 2359 Penalty 43.4 FLT 244 ddate od RDUEWR dept 1400 arrl 1529 FLT 887 ddate od EWRPTY dept 1750 arrl 2200 FLT 887 ddate od PTYGYE dept 2250 arrl 2445 PNRs rcrdloc UFSGF2 numpax 6 rcrdloc UFRKEK numpax 70

5/25/2015 Operations Research Group Continental Airlines Other Uses Integrate with Demand Driven Dispatch to swap aircraft to allow for better re-accommodation in very tight situations Proactive pre-flight re-accom to create more space on flights where too many bookings have already been taken Heads Up Tool for Scheduling to determine where extra sections may be needed

5/25/2015 Operations Research Group Continental Airlines Questions?