By Jorn Madslien
Business reporter, BBC News, Paris air show
Carbon dioxide emissions from aircraft are a significant and growing contributor to harmful global warming. It is time for the industry to sort it out, says Scott Carson, chief executive of Boeing's commercial planes division.
"The industry has to come together to commit resources and human energy, and to say that this is a priority," Mr Carson says.
Aircraft manufacturers are becoming concerned about the environment
"I think we've gotten on to the same page in a hurry," he adds, insisting that the industry spends a lot on technology, on weight reduction and on improved efficiency - and thus, reduced emissions.
"Aircraft are 70% more efficient than they were when they were first brought into the industry half a century ago," he points out.
"I think we haven't told that story well in the context of the environment."
And yet, that just is not good enough, so more needs to be done.
However, any efforts to limit the damage caused to the environment by the aviation industry are really about making priorities, according to Bill Glover, managing director, environmental strategy, Boeing commercial planes division.
For instance, efforts to reduce noise pollution generally increase an aircraft's weight and drag. This in turn pushes up fuel consumption and thus emissions, Mr Glover explains.
"There are choices to be made here," he says. "We're trying to make the best choices."
This is not always easy, since sometimes different interest groups collide, points out Jeanne Yu, environmental performance director for Boeing's commercial planes division.
"We don't want to solve a local community's noise problem at the cost of more fuel [and thus a cost to the global community]," she explains.
Design and integration
With this in mind, quick fixes involving improvements to aircraft already in the air must be combined with more thorough, long-term solutions, points out Mr Glover.
"We're looking for big steps with new products and incremental steps with current production products," he says.
Hence, it makes sense to make future aircraft from light composite materials, which require less energy to fly. Tomorrow's planes - such as the Boeing 787 Dreamliner or the Airbus A350 - will also be made more efficient by both improved design and by better integration of different components.
Tomorrow's jets will be greener, planemakers say
"You can have a great wing and a great body, but together they're just good," explains Mr Glover.
"Getting good environmental performance is about doing good on components and doing good on integration."
But it can take decades before the current fleets of aircraft are replaced by modern models.
"There are 17,000 planes out there already," says Mr Glover. "To modify all of them would be impractical and take too long."
So in the meantime it is important to work with what is there, he insists. Improvements must be made, both to existing planes and to the way they are used.
One way would be to develop new fuels, such as biofuels made from plants that could be used in existing aircraft, believes Mr Glover, though beyond facilitating meetings, Boeing believes this is a matter between fuel suppliers and airlines.
Besides, the engine manufacturers should do more, insists Mr Carson. "We're pushing the engine guys as hard as anyone else," he says.
Boeing's 787 Dreamliner is on track to make its debut in May next year
Easier solutions can be found on the ground, where working practices have been improved in recent years.
In the past, aircraft would fly with more empty seats than they do today," says Mr Glover. "The load-factor is going up," he says, hence emissions per head have gone down.
On an average flight, 80% of the seats are being used. "Ten years ago the average was about 70%," Mr Glover says.
New traffic control systems that allow for speedy take-offs and reduced in-flight waiting times, where aircraft circle, are also vital, adds Mr Carson.
"We have the technology in advanced air traffic management," he says - though upgrading air traffic control systems to make them internationally compatible is predicted to cost more than $40bn (£20bn).
Aircraft makers are not about to stump up the cash, and neither are the airlines. Indeed, nobody appears eager to pick up the tab.
Ever more flights
Widespread disagreement about who should pay for efficiency improvements in the aerospace industry means they are moving forward at a pace far too slow to keep up with the rise in traffic.
A draft United Nations report published in April says that aviation accounts for 2% of the world's carbon dioxide emissions.
And whilst the industry is only able or willing to deliver efficiency gains of more than 1-2%, it is perfectly capable of supplying both aircraft and engines, infrastructure and logistics to support an anticipated 5% growth in traffic.
As a consequence, aerospace emissions are expected to continue to rise at a rate of 3-4% per year - unless travellers themselves decide to change their behaviour and fly less.
And that, we know, is not very likely to happen anytime soon.