It is easy to imagine a perfect flight: watching our favourite film on the entertainment system, having an empty seat next to us so we can stretch out and enjoying the view from the window as we land.
For airlines, a perfect flight is very different, it involves maximising efficiency to save time and fuel and, in doing so, cutting the carbon footprint.
On May 24, Etihad Airways operated just such a perfect flight, a special Boeing 787 Dreamliner service from the carrier’s Abu Dhabi base to Washington DC.
By altering ascent and descent, perfecting the route, optimising ground handling and other measures, the 13-and-a-half-hour flight saved 4,100 litres of fuel and 10.7 tonnes of carbon emissions. Achieving this required collaboration with 30 services, from ground handling to air navigation.
To optimise altitudes and cruising speeds, liaison with air traffic started four weeks before the flight, taking into account the many other aircraft on the same route at the same time.
Winds were analysed two weeks ahead and data from previous flights was used in models to determine what the ideal flight would be like. Air traffic control provided shortcuts, optimum altitude and speed.
Christian Albrecht, Etihad vice president operations logistics, said the airline aimed for an unrestricted climb so it could reach the ideal flight altitude in the shortest time. The descent was also perfected.
“The descent was delayed for approximately seven minutes compared with a normal flight, which resulted in a direct descent – continuous descent – with no level-off, and engines in idle power at their lowest fuel use. A similar ascent and descent approach could save up to 700 litres of fuel,” he said.
The various optimisation measures, including minimising on-ground delays, added up to a fuel saving of about 5 per cent, significant on a long-haul route where typically about 100,000 litres are planned for, in addition to the mandatory reserve fuel. Such savings are significant, as fuel can constitute 30 to 40 per cent of operating costs.
In aiming for a perfect flight, Etihad is tapping into a burgeoning global area of research on flight optimisation that follows decades of effort by the industry. It is unsurprising interest is so high.
“Considering the large number of flights taking off every day from every corner of the world, even modest efficiency gains can be translated into huge savings for the industry as well as the travelling public,” said Dr Yi Gao, a lecturer at the department of aviation at the Swinburne University of Technology in Melbourne, Australia.
Technology is playing a major part in reducing fuel use, principally through more efficient aircraft. On Etihad’s perfect flight, the 787’s streamlined design, lightweight construction and modern, efficient engines can cut the fuel bill by a fifth.
Dr Gao noted that the other latest aircraft designs – among them Boeing’s 737 Max and 777X, and Airbus’s A320neo and A350 – offered improved winglet, wing and fuselage designs and have more efficient engines. Composite material, as strong as a metal frame but lighter, has been increasingly used.
Aside from innovation in hardware, a wealth of logistical factors are being looked at, including delaying departing aircraft to reduce the time they are in limbo in destination airspace.
The continuous descent used in the “perfect flight” contrasts with common practice. Air traffic control often directs aircraft to descend in stages, said Dr Gao. There is also room for improvement in the way aircraft taxi to the runway.
“A flight will not necessarily taxi the shortest possible route due to the movement of other flights at the same airport. Especially when the airport is busy, conflict avoidance takes a higher priority over efficiency,” he said.
Fortunately, this can be improved with computer-assisted instructions, as optimisation packages running on computers can calculate the ideal route, Dr Gao said.
Similar initiatives can help with flight and route planning, so as software improves, so will flight efficiency. Aircraft can also taxi with one engine idling, cutting fuel use. Better weather forecasting would also allow airlines to choose more efficient routes, in collaboration with air traffic control.
Aircraft manufacturers are researching many of these initiatives, such as Airbus with its Smarter Skies programme, which predicts that in the future aircraft could “self-organise” to choose the most efficient route. It even suggests that on popular routes, aircraft could fly in bird-like formation, cutting drag.
Dr Riko Merkert, senior lecturer in aviation management at the University of Sydney Business School’s institute of transport and logistics studies, said a “big game changer” in terms of improving flight efficiency would be optimising air traffic control.
In Europe, services are still too fragmented, he said, and in China there are too many detours because of restricted military airspace, while other parts of the world also leave room for improvement.
"It leaves huge potential for more direct and efficient flying and, hence, less fuel consumption and carbon dioxide emissions," said Dr Merkert, a co-editor of the Journal of Air Transport Management.
Other key issues he highlighted included using alternative, more sustainable fuels. As recently reported, this is a priority for Etihad through its BIOjet Abu Dhabi initiative, which has been exploring the development of a biofuel supply chain. Some experts cautioned, however, that these may have limited scope.
“Alternative fuels do offer some relief but they cannot be produced at a scale to meet future demand and they will be costly,” said Callum Thomas, a professor of sustainable aviation at the Centre for Aviation, Transport and the Environment at Manchester Metropolitan University, in the UK.
However, he said that while there are “considerable opportunities” for further improvements on operational efficiency, these are unlikely to be sufficient to counter the environmental effects of the aviation sector’s continued expansion.
Mr Albrecht, at Etihad, said that improving efficiency is not just about the introduction of more sophisticated technology but also using current technology better. The technology to achieve perfect flights exists, he said, but “it is not utilised globally worldwide in a fair and equal manner”.
Better integration of systems and improved simulation methods should, he predicted, help airlines achieve the fastest route with minimum fuel burn and carbon emissions.
“We believe that the future of flying will improve with the stronger integration of aircraft and ground systems and the ability to optimise millions of flight parameters in real time and their influence on the efficiency of a flight,” said Mr Albrecht.
So, in future, the perfect flight could become the norm rather than just a special event.