How much efficiency gain can be attributed to aircraft handling?
In a paper written in 2010 several factors are laid out in addition to aircraft design that have improved fuel efficiency and cost over the years and possible improvements in the future. Several areas were highlighted.

Routing

Opening up more airspace by more efficient usage increases efficiency.


  It is estimated that up to 8% of all aviation fuel is wasted as a result of the inefficient routes aircraft have to fly.


The paper cites flight management systems on newer aircraft as contributing toward efficiencies in routing.


  On certain oceanic routes, flight control computers are automatically plotting their own, most efficient routings with some impressive results. One airline, for example, has been working with Australian air traffic management to save almost 10 million litres of jet fuel and 772 hours of f light time in five years. It does this by exploiting the jet streams and tailwinds in the Indian Ocean.


The following charts show projected savings for implementation of NextGen air traffic systems in the US and SESAR in Europe.





Continuous climb

Being able to climb continuously to cruise altitude can save on fuel.


  A number of airports and airlines are trialling the use of so-called ‘green departures’, allowing pilots to take-off and climb to the optimal cruising altitude in one smooth, continuous ascent. This is   in contrast to the traditional method of climbing to the cruising altitude in several steps. By using this new departure method at one airport alone, some 10,000 tonnes of fuel and 32,000 tonnes of carbon dioxide were saved in one year alone.


Continuous descent

Similarly to climbing, fuel can be saved by avoiding stepped approaches.


  In trials, fuel savings of up to 40% during the approach phase have been demonstrated. This equates to between   CDO [continuous descent operations] vs stepped approach 50 and 150kg of fuel depending on the level at which CDO is commenced and the aircraft type. Up to 150,000 tonnes of fuel a year, or 500,000 tonnes of CO2, could be saved in Europe alone if CDO approaches were more widely adopted. 


Satellite based approaches and departures

Using RNAV procedures help expedite aircraft through the airport environment.


  Using satellite-based and on-board precision navigation systems such as “Area Navigation” and “Required Navigation Performance” capabilities allows ANSPs [Air Navigation Service Providers] to re-design airspace and procedures so aircraft can fly automatic fuel-saving routes into and out of the busiest airports in the world. These new departure routes have reduced departure delays of more than 2.5 minutes per flight at one airport since their introduction. Annual fuel savings are estimated at $34 million, with cumulative savings of 105 million from 2006 through 2008.


Ground handling

Fuel is saved by using single engine taxi or tugs where appropriate.

Another place more efficiency can be garnered is by installing ground electrical power to reduce APU usage.


  studies suggest that up to 85% of APU use can be reduced if groundbased electrical power systems are available, cutting the fuel bill, per gate, by $100,000 a year.


Reducing delays

Another costly problem is flight delays. Aircraft end up sitting on the ramp or taxiway burning fuel waiting for clearances.


  In the United States alone, the cost of burning fuel on the ground as a result of delays to the airline schedule amounted to over $5 billion in 2008 alone.


Conclusion

The following graph represents the potential fuel savings projected into the future broken down by technological improvements in aircraft design and fuels, operational issues such as ground handling and delays, and infrastructure such as airspace availability and routing. Of course any future projection is speculative.