Monday, 22 August 2016

Airport Congestion Zoomed In



Heathrow, the most congested European airport, has been operating at 98+% of its maximum capacity for over a decade, unable to absorb even the smallest change in airline schedules without spreading the knock-on effects across the network. This, however, didn’t stop it from accommodating more flights into its schedule and even crossing the capacity limits by overselling the slots and keeping the overbooked flights circling in holding stacks before landing. The following are some of the consequences (based on 2010 figures): 
  • 54% of 224,497 incoming flights at Heathrow were held in holding stacks 
  • By comparison, 14% of Gatwick’s incoming flights were held in stacks and 5% at Stansted (NATS)
  • 18 million arriving passengers were kept circling in holding patterns for up to 20 minutes on a normal day and 45 minutes in bad weather (NATS)
  • Airlines wasted around £65 million in fuel while stack in the holding queues
  • Airborne holding at Heathrow amounted to the equivalent of having approximately 10 aircraft grounded at airport each day. By comparison, in 2004 the equivalent of 5 British Airways aircraft a day were circling in airborne stacks above Heathrow (BA)
  • Heathrow was responsible for 91.4% of the carbon emissions from stacking aircraft in Britain as a whole, with a total of 277,900 tonnes (NATS)
(Additional cost of crew, maintenance, passengers and ripples across international and domestic networks and reduced revenue are not included)

Five years on, and the increase in Heathrow traffic continues. In 2015, compared to the previous year, aircraft movements were up by further 5% and passenger numbers by 14%, indicating the use of bigger aircraft, more fuel burned, more unproductive aircraft time, more resources, more delayed flights and lost connections for passengers and an increase in noise and air pollution. On airline side this has resulted in an unreported increase in inefficiencies, rise in costs and disruptions, and for Heathrow Airport – a rise in related aeronautical and retail revenue.

Beyond these figures are unresolved differences in the way those involved in decision making perceive congestion and make their plans, and also declarations made by policy makers and regulators that doesn’t seem to match reality:

National Air Traffic Services (NATS) ‘From an operational point of view the reality is that holding is not actually a symptom of inefficiency. In fact, Heathrow Airport schedules holding into the system. This might sound crazy but holding is actually a very efficient way of ensuring an airport with constrained runway capacity, like Heathrow, makes maximum use of the landing slots it has available.’ (nats.aero)
Association of European Airlines (AEA) ‘Stacking delays are anathema. They have a substantial environmental cost and they play havoc with the airlines' schedule integrity. They also severely impact our customers, when an on-time departure turns into a significantly delayed arrival.’




British Airline Pilots Association (BALPA) ‘The amount of stacking at Heathrow is clearly a problem and is a symptom of the capacity constraints we have. One thing that may not be figured into official holding statistics is extended flight paths pilots have to sometimes fly after leaving the stack which can add another 30 miles of flying and additional time onto the approach.’
EU framework for slot coordination ‘The aim of the EU framework is to ensure the fullest and most efficient use of existing capacity at congested EU airports while maximizing consumers' benefits and promoting the competition.’
Eurocontrol ‘Despite the prospects of slower traffic growth, Europe continues to face a severe airport capacity crunch (by 2035), which will cost airports and airlines in excess of €40 billion in lost revenues and €5 billion in congestion related disruption costs annually. ‘
McKinsey - Management Consulting ‘Increased congestion makes connecting flights more difficult to schedule and maintain—another problem for airlines as connection-heavy airports get even busier, leaving less and less room during peak connection times.' 
'Is a congested home airport a good thing for airlines? The answer is yes, at least in the short term; congested airports may give airlines an opportunity to increase revenues.’ (Excerpts from Gridlock on the ground: How airlines can respond to airport congestion)

On the improvement side, NATS is leading the way in organised actions on reducing airborne delays and increasing operational resilience at Heathrow. The problem is that whatever the expected results (which usually look bigger from local perspectives) they appear to be modest in real terms compared to the consequences of airborne stuck delays. Among the ongoing actions is the XMAN project launched by NATS in April 2014 with reported reduction of up to one minute in holding times with annual savings of 8,000t of CO2 and £1.65m in fuel - respectable but not sufficient to avoid being wiped out by even a small increase in traffic.
Similarly, the benefits of the introduction of linear holding stacks will be seriously challenged by a further increase of traffic in congested areas. “If a modern system isn’t adopted in the next decade”, said Martin Rolfe, Chief Executive of NATS, 'the average delay to each plane caught in congested airspace will increase to 15 or 20 minutes, coinciding with an increase in air traffic”.
And, in the same way, continuous expansion in congested areas reduced the expected benefits of Operational Freedoms Trial project finalised in 2013. As explained by Chief Executives of CAA and NATS during Government inquiry on aviation strategy, the focus was on the creation of more space for resilience at Heathrow rather than adding more aircraft to it – something that airports and airlines are still not ready to accept.

Will other airports follow Heathrow example? Hopefully not. The holding stacks example demonstrates how much harm the decision to force extension of capacity constrained airport in the air brings to the system. It provides some insights into what the true problems really are and indications on how they can be tackled and resolved. 

There is no shortage of ideas and action plans for improvement. The problem is that they are partial, based on past experiences, and don't take into account interactions of system components that are constantly changing. This could be overcome by applying the technique for tracking the cross-system causes of major loss making events and making necessary corrections on the go. 

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