Low cost airline easyJet has today unveiled a prototype for a new fuel efficient aircraft, or ecoJet, which it claims could deliver a reduction in CO2 emissions of 50 percent compared to existing short haul aircraft.

The company said that the new ecoJet prototype was based entirely on existing technologies and could slash emissions per passenger km to 47g based on its current aircraft configurations - potentially making it more environmentally friendly than rail and car travel. The new design would also cut noise pollution by a quarter and could be available, at a lower cost than current short haul aircraft, by 2015.

The prototype features rear-mounted "open rotor" engines that easyJet claimed would "offer unrivalled environmental performance for short-haul flying due to their higher propulsive efficiency"; a frame made from new advanced weight-reducing materials similar to those being pioneered in the Boeing 787; and an innovative design that uses wings that are swept forward in order to minimise drag and enhance fuel efficiency.

EasyJet predicted that when combined with improvements in air traffic control technology these design and engineering innovations could reduce carbon emissions by half compared with current short haul aircraft such as the 737 and A320 families of aircraft.

Speaking at a press conference to unveil the ecoJet, Andy Harrison, easyJet chief executive, insisted that the new design was "realistic" and "achievable", and in a clear signal to manufacturers said that easyJet would invest heavily in such planes. "If the 'easyJet ecoJet' were to be made available today we would order hundreds them for fleet replacement and to achieve the 'green growth' that our industry has committed to," he added.

The company insisted the first planes based on the new design could be available by 2015 if manufacturers began R&D efforts now and launched their development and flight testing programs by 2010.

The new design would result in a shorter range and slower speed than existing short haul aircraft, meaning that the same innovations could be less easily applied to the long haul sector. However, easyJet insisted that the slower cruising speed would add just 3 to 10 minutes to the average short haul journey and that the time could be made up by improvements in air traffic control and faster turn around times.

Environmentalists, however, remained sceptical about the new design's environmental impact, arguing that the expansion of the budget airline sector meant any reduction in carbon emissions delivered by more efficient aircraft would quickly be eaten up by the increase in flight numbers.

"It is important that the aviation industry looks at ways to significantly reduce its impact on climate change," said Richard Dyer, aviation campaigner at Friends of the Earth. "But unless this includes massive cuts in the anticipated growth in air travel, it is unlikely to be achieved."

However, easyJet argued that even accounting for projected growth the ecoJet alone could stabilise emissions from short haul aviation at 2005 levels until 2035. It also argued that the new design represented just the first technology "step change" and that others will follow that should reduce emissions still further.