I was wondering how airlines organise which aircraft will fly a particular route on a certain date. For example, say a BA 747 flies LHR-JFK-LHR, what happens to the aircraft when it returns to Heathrow? Will it just fly the same route again, or fly a completely different route or go into maintenance etc. What i'm trying to ask is how do airlines manage to ensure all their aircraft are at the right place at the right time? An airline such as British Airways or Delta must have a very difficult job putting a timetable together because of the huge amount of aircraft and routes they fly. How do they utilise all their aircraft effectively so that they spend as much time as possible in the air?
Hope you understand what i'm trying to ask, its sort of hard to explain it in text!
Any help is appreciated!
DEM

Good question. I often wondered myself. Thanks for asking Let's see what people say.

I'm sure they use software these days. It's not just a matter of organizing where planes go. Try figuring out which planes should be used on which routes, given performance, maintenance, fuel cost, projected passenger load, project profit on a particular flight, etc... and the problem quickly becomes unmanageable by hand. I heard that Lufthansa has recently been running computer simulations to predict how profitable the Sonic Cruiser might be. What they do is enter all the plane parameters mentioned above and simulate the planes participation in the fleet.

That's just my 2 cents. I don't work for airlines but having worked with computer simulations of
various physical phenomena, the above is my guess at how things might be done.

I think its all done on computers.

DUH! They probably have employees specially trained to do so. And computers help a lot these days. I have heard that they even set backup aircraft for all flights, in case something happens and an aircraft goes temporarily out of service. I don't mean that they have aircraft they dont use for backup, but they know exactly what aircraft will be at any airport at any time and they can make slight changes to back up flights with the least possible delay. Now that's scheduling.
Have you also wondered who makes the crew schedules for the large airlines mentioned that must have thousands of employees, including time limits, days off and seniority?

Its all done by computers (surprise, surprise!).

Basically, the flight schedule is already planned and is tagged with equipment types, and configuration where these vary within a fleet. Obviously, the equipment type can change to handle capacity variations but this isn't as common occurance as all that. Obviously, even this part of the process is not simple because if a flight is allocated to, say, a 757, the scheduler must be sure that there will be enough 757s available to fly that flight and all the others that are allocated to 757s at the same time. Its also no good the scheduler planning all inbounds to an airport on one type, and all outbounds on another! The scheduling process can also be complicated by slots at some airports.

Usually, all of the planned maintenance inputs are entered into the system too (when, which type, which aircraft / registration, where, and how long).

Also, other constraints are entered into the system, such as minimum ground stop times for each type (for which there may be differences between airports, or even between some gates at the same airport), and also other considerations such as towing time if an aircraft has to be moved from an international gate to a domestic gate, etc...

Finally, on a regular basis, the computer system allocates phyical airplanes to flights, making sure all the turn times are met and that where there's planned maintenance for a specific airplane that airplane is flown into the maintenance station.

Some airlines do dedicate specific airplanes to specific routes, but its usually more efficient if the computer allocates airplanes to flights based on equipment requirements, availability and schedule. Obviously, every bit of good planning can go to pot on the day if technical, weather delays or other problems arise.

Andy

At AA, aircraft scheduling is done inside the Marketing Department by a group called "Capacity Planning." Maintenance, Finance, Revenue Enhancement (formerly Yield Management), Crew Resources and a whole host of other work groups input their preferences, limitations, requirements, etc. All of these competing priorities are weighed against each other and ultimately balanced out in the final schedule using a combination of computer programs and human intuition. This is a continual "work-in-progress" that begins more than a year prior to the actual date of a flight and ends just about a month prior to that date.

Even though the PC helps quite a lot with the administration of the fleet and the rotation plans, there is still a human being needed who sets up the concept and framework in which the schedule will be implemented. So there is no way that a computer alone can create a schedule... it can only help to optimize the fleet utilization within a given framework!

Long haul aircraft usually don't fly only the same route back and forth. There is a detailled "rotation plan" for every single aircraft which shows the planned utilization of the fleet at any given time. Of course, due to delays, reroutings, flight cancellations there will always be ad-hoc changes to the original plan on a day-to-day basis. As Andy wrote there are many issues to observe like airport slots (usually negotiated at the IATA schedule coordination conference, the next one will take place next week in Seattle/WA btw), minimum turnaround times, curfews, maintenance and of course crew rotation.

Not too long ago, the whole scheduling process was made manually : Take a horizontal timeline of 7 days, divided into 24h each for every aircraft and draw horizontal bars in it, begin at the departure day and time, end the bar at arrival day and time. Write the flight number and dep/arr times above the bar and the origin/detination airports between these bars, then you can continue until the week is filled. Of course you have to observe the consistency of the flights, i.e. the departure airport of the next sector must always be the destination of the previous sector, except that you intend to "beam" your aircraft from one airport to the other  

Once you did this process for 10 aircraft or more you will notice how helpful a Computer program is for these rotation plans  

Programs are offered e.g. by Lufthansa Systems, by the Swedish company RM or by the Greek company AIMS.

Best regards,

Tom

It's called Tail Routing. Routing of actual aircraft determined by the Planning and Scheduling departments "wish list" as well as the maintenance bases. "Route Numbers" are the same everyday (weekends and holidays may have differing routings on them sometimes). Specific aircraft are then assigned to the routes the night previous. When an aircraft is "overnighting in a city", it is then "staged" to operate a "tail route" out of that city the following morning.

I.E. one route may just run an aircraft back and forth to a base all day:

ATL-TPA
TPA-ATL
ATL-DFW
DFW-ATL
ATL-IAD
IAD-ATL
ATL-MEM
MEM-ATL

or it may start the aircraft at the base and run it throughout the system:

ATL-PIT
PIT-LGA
LGA-PIT
PIT-MDW
MDW-MSP
MSP-MDW
MDW-ATL
ATL-FLL

In this case the aircraft is now "staged" in FLL to accept a "Tail Routing" out of FLL the following morning.

or the route may start the aircraft in an "outstation" and end it in an "outstation" (non hub, non maintenance base)....this is most common:

TUL-DFW
DFW-SAT
SAT-DFW
DFW-MCO
MCO-ORD
ORD-BGR

The airlines have various maintenance bases throughout their system, and specific tail routings are designed to overnight aircraft at maintenance bases for scheduled checks. However if an aircraft is scheduled for maintenance, or develops a situation that may require maintenance sooner than anticipated (i.e. operating on an "MEL - Minimum Equipment List"), and is not on a tail routing that will place it in a maintenance base, it can "swap tail routes" midday with another aircraft that is scheduled into a maintenance base but does not require maintenance.


I.E.

Aircraft#N888TT is scheduled for tail route # 103:

DEN-IAH
IAH-IAD
IAD-ORF
ORF-IAD
IAD-DEN

Aircraft#N889TT is scheduled for tail route #104

SFO-MKE
MKE-IAD
IAD-SDF
SDF-ORD
ORD-STL

BUT N889TT requires maintenance, and STL is not a maintenance base, SO, when the aircraft cross each other in IAD, they "swap routes", N888TT taking route 104, over nighting in STL, N889TT taking route 103 overnighting in DEN, which is a maintenance base. The aircraft are now "staged" in those respective cities for their next route assignments.

UNDERSTAND, Route Numbers, Flight Numbers, and Tail Numbers are all different things, none of which have an influence on the other.

Sounds very confusing, but it's not.....lots of training, lots of experience, and great computer programs come into play.


Hope this helps

Travis

Thanks for the replies, obviously I knew it was all done by computers, but still, all that information has to be put into the computer in the first place and i bet you need a bloody clever computer to work all the schedules out, considering factoirs such as aircraft type, crew, length of journey, routes, capacity etc. Bet it takes alot of input!
DEM

A lot of people here said "its all done by computers". It may come as a suprise to some but airlines were around before computers and these problems had to be solved even then

Interesting responses to this post.
With regard to overnight stops, do no frills airlines always plan aircraft to return to base at night to save on the cost of overnight accomodation for the crew?

Richardw,

Not always, as they need early departures from outstations as much as from home base.

VC10, I remember the massive wallboards (they are probably still used for visual checks) in op rooms of BA, Swissair, Trans International, Air Europe, Aer Lingus etc, with every aircraft shown with its schedule up to a week in advance.

The computers are merely a tool. Someone had to think up the logic behind this process. I recall from my university days that there actually is a branch (or maybe just a twig) of mathematics pertaining to "transportation problems". Basically all of the inputs go into the problem (like equipment capacity and location, passenger demand, etc), and then you go through an iterative process of asking IF . . . THEN questions until you reach the best solution.

I once worked with a programmer who wrote code for transportation problems at a railroad, he said it was the most complicated thing he ever had to deal with - I'm sure airlines are just as complicated.

As an aside, and I think it's often overlooked, but the technology the airlines use to do recordkeeping for the frequent flyer accounts is pretty advanced as well.

It depends on how much people are flying that day and how far the route is. If it is busier on one day they will switch aircraft so they can get the most people there. No it will not fly the same route or it could be bumped to a different route if the need the room.

Very interesting replies. I cannot imagine all of the factors involved, and the sheer volume of code that is needed to analyze all of the data. However, it is correct that the computer is just a tool. It has to be programmed, and someone has to know the logic behind all of this. I work on insurance software, and you guys would be surprised how large an insurance management system would be, if you consider all of the factors. I am sure that the same software that "rosters" the planes, also keeps up with dispatch reliability, efficiency, and profitability of each aircraft, and produces reports used in fleet planning and future scheduling.

The problems of airline scheduling are by no means trivial, and programming a computer to do it is quite a feat.

Branch of mathematics dealing w/ optimizing paths between nodes is called topology, and algorithms for solving these problems (ex. Dijkstra's algorithm) are far very processor-intensive and far from perfect.

I had asked this question myself many days back. do a search and u might find it.

Basically western carriers usually follow hubbed approach. and their aircraft usually return to hub before going on another flight based from the same hub.

so an aircraft that operates, say DEL-BOM will operate the return flight as well BOM-DEL. and from there will operate another return sector say DEL-HKG-DEL.

But Indian Airlines (IC) follows a different approach that allows it to service multiple sectors and maximise the use of the aircraft.

They follow a very complicated scheduling.

An aircraft that operated BOM-AMD, instead of operating the return segment may instead operate a AMD-CCU, while an aircraft that came in from DEL may operate the flight back to BOM. This way an aircraft that began its day in BOM may well end up in CCU and vice-versa.

I think Southwest (WN) of the US also follows the same approach?

This was a great question. Thanks for asking, and thanks you everyone else for the great replies.

mls515