Airport flow and Queueing system


Generally every airside and landside facility and service can be viewed as a queuing system. Passengers, aircraft, bags etc form queues at these facilities and wait to be served. Flow analysis and queuing theory provide information about a service system demand and the delays suffered by the users. (Neufville & Odoni, 20031)

Queuing system

Queuing system consists three elements: a user source, a queue, and a service facility which contains one or more identical servers in parallel. The servers have to be identical and in parallel is because even a tiny difference in, for example, distance or equipment would cause big differences in the queue waiting and processing times. (Neufville & Odoni, 20031) These three elements can be put into diagram as below:


Each user of a queuing system is generated by the user source, then passes through the queue and may remain for a period of time, and then processed by one of the parallel servers. (Neufville & Odoni, 20031) The airport check-in counters is a good example of the diagram.


The airport as a whole can be viewed as a queuing network, which is a set of service centres, each service center may contain one or more servers. After a job is served by one service centre, it may reenter the same service centre ,move to another one, or leave the system. (Yan & Veeraraghava, 20042)


The queuing process

The most obvious issue about a queue is the priority discipline. Most queues at airports follow a first come first served basis, which we call it FCFS. Which means, passengers or aircraft will line up for service according to the arrival order; however the baggage retrieval for incoming flights is somewhat random, and is called service in random order, SIRO. Also, some system divide users into classes, the best example is the boarding process. You often hear the first class and business class, or club members would be called to board the plane first, then followed by the economy class passengers in seat number order. This is a combination of SIRO and FCFS. (Scribd, 20113)

A big problem in passenger processing is, when parallel queues are formed in front of servers, whether they're allowed to join another queue if their own queue is moving relatively slower. If put barriers between queues, it sure will keep people in order, but it may lead to under utilization of some servers, where one server has processed all the passengers and left nothing to do for a while but the others are still facing many waiting passengers. At most of the airports, there's a single "S" shaped queue, when the next person has moved to the top, he can choose whichever server that's available, therefore to ensure there's only one user in front of each server, but all servers are operating in a similar pace. Airport queuing system should be fairly reliable to ensure the smooth operation, number of servers and length of the queues are critical to the whole airport system.

Stupidly Long Unnecessary Queue at Heathrow Airport

Video embedded from YouTube on 15 October 2011

The psychology

Psychological factors plays an important role in the queuing systems, it can also help to ease the unavoidably negative reactions of air travelers to airport delays by influencing their perceptions of the situation.

  • Physical environment A comfortable environment, such as seating availability, temperature, is a central influence on perceptions about delays, passengers will be more tolerated to the situation and reduce negative react from happening.
  • Information Passengers will be more patient and feel safer to the situation if they have been updated with information constantly, this can either be rolling words displayed on the screen or radio. When people have more knowledge about what is happening, they become more confident to control the sudden incidence such as a major delay, or easier to make changes to their original plan.
  • Fairness This often happens with the parallel queues, where A received services before B, who arrived before A but in a slower queue, in this situation, B will feel unfairness occurred. Snake queue is the best solution to control fairness. (Neufville & Odoni, 20031)

What the passengers can do to help

well, it's simple.


And since airlines introduced internet check-in, cellphone boarding pass and self check in machine at the airports, use them. They will deliver faster and easier one on one service to you, and they will reduce the size of the queues waiting in front of the counters. Some travel-light passengers are even able to skip many processes at the airport and board their planes a lot quicker than usual, firstly, they have no luggage to claim, therefore no need to wait in the queues to hand in luggage, they are able to print out boarding pass at home or use cellphone text boarding codes.

Self check-in machine


Internet check in


Cellphone boarding code

1. Neufville, R. & Odoni, A. (2003).Airport systems.USA: The McGraw-Hill Companies.
2. Yan, T. & Veeraraghava, M. (2004).Networks of queues.Retrieved from on 15 October, 2011
3. Scribd. (2011).Queuing theory.Retrieved from on 15 October, 2011
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Want to know more?

Wikipedia queuing theory
The psychology of waiting lines
Heathrow to pay GBP500,000 penalty for queues
Long queues at airports creating 'new targets for terrorists
Airport Queuing Time Measured With Bluetooth

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