One of the key challenges facing aviation today is that the speed of realising new airport developments – whether that’s new runways or terminals – is being outpaced by airline demand. That’s why managing and maximising airport and airspace efficiency has become so important.

The benefit is that capacity or resilience can often be boosted without the operator having to invest huge amounts of money in new infrastructure and development. It’s an approach that’s seeing NATS being invited to work at airports all around the world.

But, in order to do so you need to truly understand what capacity is and how it’s made up…

What actually is capacity?

From the operation of the airspace and runways through to the flow of passengers through the terminals, airport capacity is a complex issue that hinges on a whole range of factors.

For example, the number of passengers you can get through a terminal is constrained not just by how many people you can physically fit in the building, but also by health and safety regulations, how many bags the baggage system can process and how many immigration and passport control facilities there are and so on.

The same is true on a runway. What are the required separation distances between aircraft on final approach? What’s the mix of aircraft types using the runway? Are the runway exits in the best locations? Do the departure routes diverge allowing the required spacing to be achieved quickly after take-off? Again, the list goes on. The declared capacity of an airport has to consider all of these factors and is limited by the most constraining.

Ironically, more often than not an airport’s runways are not only its most expensive assets but its biggest capacity constraint.

Aircraft queuing at Changi Airport, Singapore. NATS has been working at the airport to help increase capacity. Image by  Simon_sees vis Flickr

Aircraft queuing at Changi Airport, Singapore. NATS has been working at the airport to help increase capacity. Image by Simon_sees via Flickr

Capacity versus resilience

The simple fact is that there is always a trade-off between capacity and resilience. For an airport that schedules to a level near to or at its capacity, the level of resilience is going to be lower than at an airport that plans in a measure of spare capacity or breathing room.

The trick is to get the balance right. Typically something like a 5-10% decrease in scheduled movements every 4-5 hours takes capacity out, but can also be very effective in allowing an airport to recover from periods of moderate disruption. Without it, delays can build up very quickly with cancellations often being the only option.

Capacity and performance

The last, but probably the most crucial factor when determining airport capacity is performance – not only the air traffic control service but also the pilots. Both have to work together in order to routinely deliver the airline schedule on time.

At a busy airport, controllers have to tactically manage the traffic demand, balancing arrivals and departures to ensure that the operation is working as well as possible at all times. For example, if the spacing between aircraft on final approach isn’t delivered consistently, then larger gaps will lead to increased levels of delay and lower runway throughput. Only when everything is working together in harmony can you deliver peak capacity.

We routinely look at UK airspace and airport performance to benchmark how well each component of the ATC system is operating, looking for any inefficiency and using simulation tools to work out how to make improvements.

I’ll be talking more about the exact techniques that we use in my next post.

In the meantime, if you’ve got any questions or want to understand more about what we do, leave a comment on get in touch.

[Header image by Angelo DeSantis via Flickr]


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Really a great blog post about airport capacity and terminals. Thanks for sharing with us.


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