"A US company says it has successfully completed test flights of a potentially environment-friendly aircraft powered by liquid hydrogen."
"The aircraft, called Global Observer, looks more like a glider than a conventionally powered plane, with its wingspan of over 15m, small fuselage slung underneath and extended, "dragon-fly" tail."
"Greenhouse gas emissions from air travel are growing faster than those from any other economic sector.
In 1999, the Intergovernmental Panel on Climate Change (IPCC) - the body which collates and evaluates scientific evidence on climate and distils it for policymakers - calculated that aviation contributed around 3.5% to human-induced global warming.
Passenger travel is now growing by 5% per year, with air freight expanding even faster, at 6% per year. Even with improvements in efficiency, the IPCC believes aviation's global warming contribution will be between 2.6 and 11 times greater by 2050.
New technology which avoids hydrocarbon fuels and their carbon dioxide emissions could be an important way of curbing this trend.
But the advantages of hydrogen power have not been established definitively. Fuel cells produce water vapour, which is itself a greenhouse gas.
Released several kilometres up in the atmosphere, it is not clear how the global warming impact from this technology would compare with emissions from conventional engines."
