Crew scheduling - Airline Industry

Nabil Si Hammou

National Institute of Statistics and Applied Economics

INSEA

Internship within Royal Air Maroc, 2005

Operations Research Student

[email protected]

Crew Scheduling:

Modeling and solving the crew scheduling problem

Crew Scheduling:


Plan

Context and objective of the project

Problem analysis

Modeling and solving methods

IT Development

Simulation and test

Conclusion

Royal Air Maroc

Royal Air Maroc ( RAM) was created in 1957 in order to provide air transport services for travelling passengers and freight.

Currently, it represent one of the biggest Airline companies in Africa with more than 1 billion euro of sales annually .

The annual staff cost represent more than180 millions euro. It affects relatively the finances of the company.

The activity is divided in 4 business lines

TransportationTransportation

ManufacturingManufacturing

Hotel businessHotel business

ServiceService

3Internship within Royal Air Maroc, 2005

Context: ground operations

4

Regarding the transportation activity, in addition to flight operations , Royal Air Maroc cover the processing of the ground operations related to the passengers and the aircraft at the Morocco Airports. In particularly for the Casablanca International Airport, more than 290 agents are in charge of the execution of ground operations.

Ground operationsGround operations

290 agents

Loading and unloading of luaggage

Loading and unloading of luaggage

Transport of passengers between aircraft and

terminal

Transport of passengers between aircraft and

terminalConveyance of aircraftsConveyance of aircrafts

Fuel Loading Fuel Loading

1 2

3 4

OthersOthers5


Context: Resource Management

The human resource management related to the ground operations is based on the flight planning and traffic forecasted

Flight planning, traffic forecastedFlight planning, traffic forecasted

Execution and

Recovery

Execution and

Recovery

Manpower PlanningManpower Planning

Crew schedulingCrew scheduling

Human Resource ManagementHuman Resource Management


Context: Resource Management

At the end of each month, given a flight planning and traffic forecasted of the next month, the manager of ground operations estimate the number of resource needs for each couple (day, shift ) during the next month.

At the end of each month, given a manpower planning established, the ground operation manager builds a monthly schedule for all ground operation agents in order to meet the needs of the company. In an other hand, the schedule should also respect the work regulation requirements .

1

2

3

1

2

The ground agents execute the handling activity and the manager makes sure that the operations are executed as well as planned. In case of any disruption, the manager adjust the schedule and establish a recovery plan

3


Context: Crew Scheduling

Because of the lack of a powerful software, the person in charge of crew scheduling plan manually in an Excel spreadsheet the work of each agent of the 290 ground agents during all days of the next month

This management is a major handicap for the

company and generates an addit ional

cost against the overall strategy to reduce

costs.

This management is a major handicap for the

company and generates an addit ional

cost against the overall strategy to reduce

costs.

Trail-and-error method

Trail-and-error method

schedulingscheduling

Objective

Within a strong competitive environment in the Air Transport field, the optimization of resource has become an essential source of growth.

The main objective of the project is to develop and implement a specific solution for crew scheduling problem in order to optimize the ground operations costs.

The new approach of human resource management should bring substantial benefits in the short term for both resource management rationalization and cost reduction

The project is formed by four main stage:

Modeling & Solving Methods

Modeling & Solving Methods

Test & Simulation

Test & SimulationDevelopmentDevelopment

Stage 1 Stage 2 Stage3

Problem AnalsysisProblem Analsysis

Stage 4


The ground operations last all the day 24h/24h and all the week7d/7d. Due to the traffic structure in the airport, Royal Air Maroc have defined three working hours for ground operation agents :

From 06h to 15hFrom 14h to 23hFrom 22h to 07h

At the end of each month, given resource need expected, the ground operation manager establish a monthly schedule for all ground operation agents in order to meet the needs of the company. The schedule should also respect the work regulation requirements.

The person in charge of scheduling plan manually in an Excel spreadsheet the work of each agent of the 290 ground agents during all days of the next month. By using Trail-and-error method , he try to optimize the number of agents assigned for covering the ground operation activity.

Because of the scheduling takes into account many parameters and constraints, it’s almost impossible to find the optimal solution by using Trail-and-error method.

Problem analysis


10

Problem analysis

Demand ConstraintDemand Constraint

Scheduling rulesScheduling rules

Regulation work Constraint

Regulation work Constraint

ConstraintsConstraintsObjectiveObjective

Minimize the number of the resources assigned

Minimize the number of the resources assigned

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Problem analysis

At most, one shift per dayAt most, one shift per day

The maximum working hours per month : 180hThe maximum working hours per month : 180h

Two free days after working night shift

Two free days after working night shift

06h-15h06h-15h

14h-23h14h-23h

22h-07h22h-07h

For each person:The total number of shift worked: is less than 20

Problem analysis

Regulation work constraintsRegulation work constraints

ConstraintsConstraints


12

Problem analysis

For each couple ( shift , day) the number of agents assigned should be more than resource needs for this couple

Scheduling

Scheduling

Resource needs

Resource needs

DemandDemand

ConstraintsConstraints


13

Problem analysis

Minimize the number of the resources assigned Minimize the number of the resources assigned

Free

Free

ObjectiveObjective


14

{ { } { } { }4..130..1..1j jourday theduring k state the toassigned is i""agent theif 1elseif 0,, ∈∀∈∀∈∀= kjNiX kji

{ { }NiYi ..1day oneleast at worksi"" agent theif 1elseif0 ∈∀=

Modeling:

22h-07h22h-07h

freefree14h-23h14h-23h

06h-15h06h-15h Or

Or

Or

Decision variables: agent assignment in the day


15

The constraint requires that each agent could work at most one shift per day is expressed by :

The constraint requires that the number of agents assigned for each couple shift , day must satisfy the resource needs is expressed by :

The constraint requires that the total hours working for each agent during one month is 180 hours is expressed by :

This constraint express also that an agent is assigned only if he works at least one day during the month

{ } { }

kshift theduring jday in the needs resource The

3..130..1

,

,,,

=

∈∀∈∀≥∑kj

ikjkji

Dwith

kjDX

{ } { }30..1..114,,3,,2,,1,, ∈∀∈∀=+++ jNiXXXX jijijiji

{ }NiYX ij k

kji ..1*2030

1

3

1,, ∈∀≤∑∑

= =

Modeling: Constraints


16

The constraint requires that if an agent works a night shift , he must be free in the two next days, is expressed by :

{ } { }{ }NiXX

jNiXXX

ii

jijiji

..1

28..1..1)(*2/1

4,30,3,29,

4,2,4,1,3,,

∈∀<=

∈∀∈∀+<= ++

Modeling: Constraints


17

∑=

=

Ni

iiYMin

1

Modeling: Objective

The objective is to minimize the resources assigned to cover the activity


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{ } { }30..1..114,,3,,2,,1,, ∈∀∈∀=+++ jpijiXjiXjiXjiX

{ } { } { } { }{ } { }NiY

kjNiX

i

kji

..11,0

4..130..1..11,0

:With

,,

∈∀∈

∈∀∈∀∈∀∈

{ }NiYX ij k

kji ..1*2030

1

3

1,, ∈∀≤∑∑

= =

{ } { }{ }NiXX

jNiXXX

ii

jijiji

..1

28..1..1)(*2/1

4,30,3,29,

4,2,4,1,3,,

∈∀<=

∈∀∈∀+<= ++

∑=

=

Ni

iiYMin

1

{ } { }3..130..1,,, ∈∀∈∀≥∑ kjDXi

kjkji

Modeling: Model

Solving crew scheduling problem become equivalent to solve the following mathematical model


19

In order to better solve the mathematical model, we have compared different methods could be used

Through the comparative study and the analysis of the context of our project(the implementing time ,the size of the problem…), we have decided to use Brunch and Bound Method for solving the mathematical model of the crew scheduling problem

Solving methods


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Development (1)

Resource needs

Resource needs

SolverSolver

Extraction

of data and creation of model

Extraction


Solving mathematical

model


model

ScheduleSchedule

Displaying

Schedule

Displaying

Schedule

20

1 2 3

The IT program could be divided in 3 parts :


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Development (1)

Resource needs

Resource needs

SolverSolver

Extraction


Extraction



model


model

ScheduleSchedule

Displaying

Schedule

Displaying

Schedule

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1 2 3

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Excel spreadsheet

Excel spreadsheet

VB programVB program

The Extraction of data is made through a program we have developed under visual basic. The program loads data ( resource needs) from an Excel spreadsheet and it creates a mathematical model should be transferred to the solver

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Development (2)

Resource needs

Resource needs

SolverSolver

Extraction


Extraction



model


model

ScheduleSchedule

Displaying

Schedule

Displaying

Schedule

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1 2 3

LINGOLINGO

For solving the mathematical model , we have used an American solver equivalent to Cplex.


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Development (3)

Resource needs

Resource needs

SolverSolver

Extraction


Extraction



model


model

ScheduleSchedule

Displaying

Schedule

Displaying

Schedule

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1 2 3

VB programVB program SchedulingScheduling

The display of the schedule is made through a program we have developed under visual basic. The program recover the solution of the mathematical model from the solver results and it transforms it to an understandable scheduling in an Excel file

Simulation

Due to the organization within ground operation department, we have tested the program for crew scheduling of many subgroups of ground agents. The size of subgroup is between 30 and 50 agents.

We have compared the crew scheduling results established by using our approach based on operations research and the current method adopted in the department (Trail-and-error method).

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Solving time

Solving time 1 hourSolving time 1 hourAfter 9 hours, the program is still

executed. The solution have been found one hour later

After 9 hours, the program is still executed. The solution have been found

one hour later

After executing the program many time, we have found that the solving time of each scheduling is generally between 1h and 10h.

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Conclusion

After testing the program many time, It appears that the use of the approach suggested based on the operation research approach could reduce the ground operation cost by more 11%( mainly, 3 people for each subgroup of thirty people)

The development of a specific tool for crew scheduling has demostated its interest because of:

Respect of all constraint : regulation work and internal rules and demands,

Flexible to additional constraints

Consistent to the global strategy of the Group.

An update of these models for adapt the system to the changing context (situation, strategy group, ...) seems essential.


Nabil Si Hammou

National Institute of Statistics and Applied Economics

INSEA


Operations Research Student

[email protected]

Crew Scheduling:


Crew Scheduling:


Crew scheduling - Airline Industry

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