Aircraft and engine designers are investing in fuel efficient aircraft.

CNN: Flight of biofuel fancy?

But the shift towards synthetic fuel has provoked criticism, because when such fuel is made from coal and then burned in an aircraft engine, more greenhouse gases are emitted overall than would be produced if the aircraft simply burned conventional fuel derived from oil.

ECONOMIST: Monitor

He singled airplane manufacturer Sukhoi Company, saying Russian made aircraft should be competitive with their foreign rivals in terms of engine noise, fuel economy and flight distance.

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In jet aircraft, purifying cabin air would save on fuel needed to compress fresh air bled from the engine to ventilate the cabin.

FORBES: Companies & Strategies