By Nigel Cassidy
Business reporter, BBC News, Farnborough
Manufacturers are looking for a solution for both noise and emissions
For 59 of the last 60 Farnborough International Airshows, nobody really had to worry about the price of aviation fuel.
Yet now, with the underlying cost of oil having doubled since the last Farnborough in 2006, the entire industry is focusing on how to make conventional jets burn and waste less fuel.
Even the military are starting to worry about it.
For the commercial sector, part of the answer lies with improving air traffic controls, modifying aircraft handling and fitting 'winglets' to reduce drag.
Yet, a glance round the vast technical exhibition halls at Farnborough confirmed that the focus is now moving more closely onto the features and benefits of the next generation of jet engines that will be available for the plane makers to choose from.
One magic figure being bandied about seems to be 20%.
That's the percentage of fuel saving that cash-strapped European and US airlines now seem to be demanding before promising to shell out upwards of £25m for a typical new narrow-bodied jet.
None of the 'big four" engine-makers - Rolls-Royce, Pratt & Whitney, GE and CFM - can quite help them achieve that yet.
Particular industry hopes rest on Pratt and Whitney, part of United Technologies, which is making a big splash again this year with its "geared turbofan" engines.
The company has already invested $1bn in the technology and a test engine is also about to be tried out on an Airbus.
Innovative use of gearing allows the main front fan and the rear sections of the engine to operate at different, optimum speeds.
"The result of that is much better fuel burn, much lower noise, much lower emissions," says Bob Keady of Pratt and Whitney.
"It is a complete solution, we believe, for the industry."
The geared turbofan has already been chosen to power the new Bombardier 135 C series regional jet and has been selected by Mitsubishi for its new airliner.
Competitors have some doubts about whether Pratt's gearbox concept will be reliable and about the ongoing cost of maintenance.
GE's Chet Fuller believes his own firm's new generation of "eCore" engines will offer aircraft operators "up to 16% better fuel efficiency over GE's best engines today".
"We think that we can have a better fuel burn with a simpler architecture that is based on having a much more efficient engine core," he says.
Meanwhile, Rolls-Royce, GE, and CFM are all also thought to be working on new ideas for " open rotor" engines.
These may offer the speed and performance of a turbofan, with the fuel economy of a turboprop. However past examples were far too loud in flight and would not meet present day noise regulations.
It is intriguing that newer players like Bombardier are already specifying geared turbofan engines.
Boeing and Airbus customers may have to wait.
Pratt & Whitney clearly hopes that if its concept is proven, airlines may press the market leaders to switch to leaner burning engines more quickly.
Analysts are optimistic that the industry will deliver on all this as it has done since its inception.
"Never under-estimate the ability of monetary factors to motivate the industry," says Paul Edwards, head of aerospace for the consultants Jefferies International.
"The current fuel price is a far greater incentive for engine-makers than all the previous exhortations to help reduce carbon footprints. Yet the technical hurdles are immense so real solutions could be 10 or 15 years out."