Airline Operations Lecture #1 1.206J April 23, 2003 Outline ? Airline planning complexity Schedule disruptions Schedule dependability CDM Ground Delay Program How do airlines recover the schedule? Traditional ARM; Model shortcomings Interdependency of passengers and aircraft operations Airline planning Optimized schedule designs have resulted in squeezed schedule with little slacks (i.e., idle time) For examples: GBE FAM with TW: less aircraft slacks GBE Extended Crew Pairing Problem: less crew slacks Plan is more inclined to be disrupted Ongoing research in robust planning: are airlines ready to pay the cost? Feasibility constraints Aircraft maintenance checks Pilot work rules Flights Passengers Aircraft maintenance checks A: roughly once a week -- on average approximately every 60 flight hours B: once a month -- roughly every 300 to 500 flight hours C: Entire aircraft check GBE Narrow body: once a year; “Light C Check” (3 days) “Heavy C Check” (3 to 5 weeks) GBE Wide bodies: every 15 to 18 months; “Heavy C Checks” (2 weeks) Pilot work rules (FAA regulation Part 135) 1,200 hours in any calendar year. 120 hours in any calendar month. 34 hours in any 7 consecutive days. 8 hours during any 24 consecutive hours for a flight crew consisting of one pilot. 8 hours between required rest periods for a flight crew consisting of two pilots qualified under this part for the operation being conducted. 9 consecutive hours of rest for less than 8 hours of scheduled flight time. 10 consecutive hours of rest for 8 or more but less than 9 hours of scheduled flight time. 11 consecutive hours of rest for 9 or more hours of scheduled flight time. Flight regulation You need a feasible aircraft and a crew to operate a flight Airports with slots GDP Airport curfew (e.g., Orange county, SNA) Rule 240 Contract of carriage (AA) “If your flight is delayed, cancelled or you miss a connecting American Airlines flight, due to a schedule irregularity GBE American Airlines must confirm you on their next flight (on which space is available) at no additional cost. GBE If there is an alternate American Airlines flight that will arrive at your destination earlier than the alternate you have been offered, you have the right to be confirmed on this American Airlines flight at no additional cost, even if first class space is all that is available. GBE If the alternate American Airlines flight is not acceptable to you, you have the right to be confirmed on the flight of a different airline at no additional cost. GBE If there is an alternate "different airline" flight that will arrive at your destination earlier than any alternate flight you have been offered, you have the right to be confirmed on this flight at no additional cost, even if first class space is all that is available. GBE If no alternate flight (on American Airlines or a "different airline") is acceptable to you, American Airlines must refund your money - even if you have a non-refundable ticket.” Schedule disruptions Schedule disruptions: GBE Aircraft: not on the schedule route GBE Crew: violates rules GBE Passenger: canceled flight or missed connection Shortages of airline resources: GBE Resource schedule dependability GBE Aircraft mechanical problem GBE Crew unavailability (misconnections) Shortages of airport resources: GBE Inclement weather: reduction in airport runaway capacity; affect all aircraft flying through the airport GBE Airport security A dozen of disruptions happen on average every for Continental Airlines Schedule dependability Delay chain Arrival delays, especially those that occur early in the day, tend to propagate in the network. Flight 6:00 7:00 8:00 9:00 10:00 11:00 12:00 A B C D Scheduled Actual Attendants Crew Aircraft Local Arrival and Departure Times 13:00 Banked hub airport In US, no schedule restrictions at all but 4 airports (which ones?) Major airlines use to schedule more flights than maximum airport hub airport capacity When adverse weather conditions happens, flight operations under IFR rules, greater Miles In Trail (MIT): minimum separation distance between two aircraft in terminal area When volume too high in a sector, flights are slowed down or delayed on the ground (Ground Delay Program) 0 5 10 15 20 25 30 35 40 45 5678910112131415161718192021223 N u m b e r o f o p er at i o n s p e r 15m i n u t es Total Departures Total Arrivals VFR conditions IFR conditions Air Traffic Control System Command Center Air route traffic control centers Terminal radar approach control - TRACON Air traffic control tower Ground Delay Program (GDP) When capacity shortage is too large, ATCSCC issue a GDP to prevent airborne holding of arriving aircraft. (safety, workload, fuel) Instead, aircraft are better off waiting on the ground Example: Yesterday in BOS: ‘Due to EQUIPMENT, RY 4R GS OTS/LOW CIGS/VSBY, there is a Traffic Management Program in effect for traffic arriving BOS. This is causing some arriving flights to be delayed an average of 1 hour and 3 minutes with some arriving flights receiving as much as 1 hour and 38 minutes delay.’ How does a GDP work? GDP (Cont.) Compare Airport Arrival Rate (AAR) to scheduled flight demand Calculate delay for each arriving flight, First Scheduled First Served (FSFS) Issue Expected Clearance Departure Time (ECDP) What are potential problems with this approach? Collaborative Decisions Making (CDM) - GDP Data exchange between ATCSCC and the Airlines Operations Control Centers (AOCC): CDM-Net Ration by schedule: gives more control to airlines to assign flights to slots Compression: removes disincentives to providing schedule updates Compression benefit example How Important is Schedule Recovery? G06Estimates of the cost of airline disruption range from 2% to 3% of annual revenues G06Delta reports 8.5 million passengers affected, $500 million lost per year G06Total industry revenue is over $300 billion per year G06Disruption costs range from $5 to $10 billion per year How do airlines recover the schedule? Airline Operations Control Center (AOCC): centrally manage operations of aircraft, crews and passengers Monitor flight irregularities, implement recovery plans Quickly return the schedule to on-time after major disruptions AOCC G32G53G48G55G44G57G4CG52G51G56 G27G4CG55G48G46G57G52G55 G26G55G48G5A G33G4FG44G51G51G48G55G56 G26G55G48G5A G26G52G52G55G47G4CG51G44G57G52G55G56 G27G4CG56G53G44G57G46G4BG48G55G56G0F G35G52G58G57G48G55G56G0F G2FG52G44G47 G33G4FG44G51G51G48G55G56 G26G58G56G57G52G50G48G55 G36G48G55G59G4CG46G48 G26G52G52G55G47G4CG51G44G57G52G55G56 G32G53G48G55G44G57G4CG52G51G44G4F G38G51G4CG57 G32G53G48G55G44G57G4CG52G51G56 G50G44G51G44G4AG48G55 G2FG44G55G4AG48 G44G4CG55G46G55G44G49G57 G2AG55G52G58G53 G24G4CG55 G57G55G44G49G49G4CG46 G46G52G51G57G55G52G4F G4AG55G52G58G53 G32G53G48G55G44G57G4CG52G51G56 G50G44G51G44G4AG48G55 G36G50G44G4FG4F G44G4CG55G46G55G44G49G57 G4AG55G52G58G53 G26G55G48G5A G33G4FG44G51G51G48G55G56 G26G55G48G5A G26G52G52G55G47G4CG51G44G57G52G55G56 G27G4CG56G53G44G57G46G4BG48G55G56G0F G35G52G58G57G48G55G56G0F G2FG52G44G47 G33G4FG44G51G51G48G55G56 G26G58G56G57G52G50G48G55 G36G48G55G59G4CG46G48 G26G52G52G55G47G4CG51G44G57G52G55G56 G32G53G48G55G44G57G4CG52G51G44G4F G38G51G4CG57 Current Practice Operations Coordinator Delays, Assigns Equipment Passenger Coordinator Fleet 2 Aircraft Coordinator Fleet 2 Crew Coordinator Fleet 1 Crew Coordinator Fleet 1 Aircraft Coordinator “Can’t Do It!” “Shouldn’t Do It” Operations Controllers GUI: Gantt Chart AOCC decisions to recover the schedules Recovery priority: GBE Aircraft > Crews > Passengers Decisions: GBE Aircraft route swaps with no crew schedule disruptions enable to absorb flight delays GBE Flight cancellation: Hub-and-spoke schedule enable almost always to find cancellation tour with only two flights. Especially interesting when 2 flights belong to the same planned crew duty GBE Call reserve crews Airline operations recovery: challenges Airlines’ plans are sophisticated GBE Aircraft, crews and passengers have different route schedules GBE The objective of planning is to minimize operating costs, which result in maximizing resource utilization, leaving very little slack to recover disruptions Following a disruption, choosing the best operational decisions are hard because: GBE Size of the decision space GBE Real time; If wait too long, solutions might become obsolete GBE Complex restrictions (FAA, contractual) GBE interdependencies between airline resources and passengers Challenges (Cont.) Impact of delay depends on the state of the complex multi layer plan at a given time: GBE 30 minutes flight delay may result in crew disruption, flight cancellations and severe passenger disruptions. The effect can last for more than a day GBE Conversely, a 30 minutes delay might benefit crews and passengers as both would have been disrupted had the flight departed on time What is the objective? GBE Can we assign a cost to one minute of flight delay? GBE Can we assign a cost to a flight cancellation? Airline Integrated Recovery G83 Schedule Recovery Model (SRM) G83 Aircraft Recovery Model (ARM) G83 Crew Recovery Model (CRM) G83 Passenger Flow Model (PFM) G83 Journey Management G83 Passenger Re-accommodation G36G35G30 G24G24G35G35G30G30 G26G26G35G35G30G30 G33G33G29G30G29G30 G33G44G56G33G44G56G56G56G48G51G4AG48G48G51 G48G55 G55G35G48G35G48G44G44G46G46G46G52G50 G46G52G50G50G50G52G47G52G47G44G44G57 G57G4CG4CG52G52G51G51 Airline Schedule Recovery Problem: Assumptions At a given time of the day, we assume that airline controllers know the state of the system: GBE Locations and availability of resources Aircraft Pilot and flight attendant crews GBE Passenger states (i,e., disrupted or not) and locations/destinations Airline Recovery Model, ARM (G. Yu et al.) tt ff ff fFtT fF f t ff tT f tt tt ff ff fF fF dj oj 00 ff 0 0 fF oj __ ff _ fF dj min d x c z st : xz1 xy xy xy j xy Flight coverage Aircraft balance Initial resource at ai Ops cost + Cancellatio rports n cost ∈∈ ∈ ∈ ?+ ∈∈ + ∈ ? ∈ ?? ×+ ×?? ?? += += + += + ∑∑ ∑ ∑ ∑∑ ∑ ∑ tt ff j x{0,1};y0 End of the day resource at airports ? = ∈≥ Objective is to minimize operating cost (flight delay and cancellation costs) Aircraft route schedule S1 H S2 Aircraft A Aircraft B Passenger itinerary schedule S1 H S2 Aircraft actual operations: unexpected delay (e.g., aircraft technical problem) S1 H S2 delay Aircraft A Aircraft B Operations decision #1: cancel S1 H S2 delay Aircraft A Aircraft B Operations decision #2: don’t cancel; don’t postpone aircraft B S1 H S2 delay Aircraft A Aircraft B Operations decision #3: don’t cancel; postpone aircraft B S1 H S2 delay Aircraft A Aircraft B Operations decision #1: cancel Passenger actual itineraries S1 H S2 Aircraft A Aircraft B Passenger actual itineraries Operations decision #1: cancel S1 H S2 Passenger actual itineraries Operations decision #2: don’t cancel & don’t postpone aircraft B S1 H S2 delay Passenger actual itineraries Operations decision #3: don’t cancel & postpone aircraft B S1 H S2 delay Aircraft A Aircraft B ARM shortcomings What cost to assign to flight cancellations and flight delays? GBE Objective coefficients are fixed in the ARM but in actual operations they actually depend on the overall solution, for example: Postponing a flight departure might reduce overhead crew cost and passenger delays and or conversely might disrupt crews and increase total passenger delay A flight cancellation can benefit the passengers and reduce airline operating cost or conversely a flight cancellation can result in severe overhead costs to the airline GBE Testing using actual airline data showing that the solution is highly sensitive to the objective coefficients The airline operations recovery problem: our objective Reduce total passenger delay and the number of disrupted passengers by deciding on: GBEFlight departure times (or clearance) GBEFlight cancellations if necessary while satisfying resource feasibility (crew and aircraft restrictions) and controlling actual operating costs Example’s conclusion Decision #3 is the best decision for passengers The ARM would chose either decision #1 or #2 depending on the flight delay and cancellation cost coefficients: GBE The best decision for the passengers will never be chosen by ARM GBE Passenger direct operating costs not capture; overnight passengers create extra direct costs for the airline (e.g., hotels) and potential lost revenues GBE No passengers are disrupted in decision #3 Postpone flights, aircraft A only #2 Postpone both aircraft A and aircraft B #3 Cancel 2 flights, aircraft A #1 DescriptionOperational decision Questions? Discussion items?