By Stephen Dowling
An Airbus A380 has already flown on alternative fuel
On Sunday, a Virgin Airlines Boeing 747 took off from London's Heathrow Airport en route to Amsterdam. This short flight may prove to be a giant leap forward for the aviation industry.
The aircraft did not carry passengers - but it was the first commercial aircraft to fly partly under the power of biofuels.
One of the aircraft's four engines ran on fuel comprising a 20% biofuel mix of coconut and babassu oil and 80% of the normal Jet A aviation fuel.
Biofuels - principally ethanol and diesel made from plants - are one of the few viable options for replacing the liquid fuels derived from petroleum used in transport, the source of about one quarter of the human race's greenhouse gas emissions.
The airline industry is being increasingly criticised for its perceived part in global warming, as more and more people take advantage of cheap tickets on aircraft powered by kerosene. Environmentalists claim it is a major carbon producer, fuelling rising world temperatures.
Airlines and aircraft designers have been feeling the heat. Plane-makers Boeing and aircraft engine manufacturers General Electric have been working with Virgin to cut down their flights' carbon footprints.
What is exciting the aviation industry is the fact the aircraft is completely unchanged, using the same engines as any scheduled, passenger-carrying flight. Only the fuel is different.
The flight follows a journey made by an Airbus A380 earlier this month using another alternative fuel - a synthetic mix of gas-to-liquid - in one of its four engines.
It flew from Filton in the UK to Toulouse in France, a journey of some 900km (560 miles), and was in partnership with Rolls-Royce and Shell.
Virgin's chief Richard Branson wants biofuel in his planes
Air New Zealand is also working with Boeing and Rolls-Royce to mount a test flight powered partly by biofuels later this year.
These are the first tentative steps in breaking the aviation industry's reliance on kerosene. But it is likely to be decades before aircraft are able to take to the skies powered entirely by something other than fossil fuels.
One industry analyst told the BBC News website there were several problems to overcome.
Jet A fuel, one of the standard aviation fuels, has a stable energy content and a low freeze point - meaning it is suited to the very low temperatures encountered by high-flying aircraft.
Biofuels cannot be relied upon to operate as reliably in the same temperatures.
Jet A fuel also burns consistently, which means it provides a reliable and safe fuel source for long flights.
Airlines also want a biofuel which can be burnt in existing engines - rather than having to replace every engine in their fleets.
There are other issues surrounding biofuels. There are concerns widespread planting and use of biofuel crops could threaten natural ecosystems and raise food prices. It could also mean the deforestation of rainforests, which absorb massive amounts of carbon.
Refined kerosene powers today's planes
Virgin remained tight-lipped about where its biofuel comes from until the day of the flight but said it would be a "truly sustainable type of biofuel that doesn't compete with food and fresh water resources".
Some environmentalists are sceptical. They believe the secret to cutting down aviation's share of the carbon is cutting the amount of flights we take.
Kenneth Richter, Friends of the Earth aviation campaigner, said: "Biofuels are a major distraction in the fight against climate change. There is mounting evidence that the carbon savings from biofuels are negligible.
"If Virgin was really serious about reducing the aviation industry's impact on the environment it would support calls for aircraft emissions to be included in the Climate Change Bill."
Green Party councillor and former chemist Andrew Boswell said: "Richard Branson is making a huge mistake backing biofuels.
"It means a huge amount of fuel we've got to produce."
Mr Boswell, who campaigns for the lobby group Biofuel Watch, said it was unsustainable to try and replace transport's share of fossil fuel consumption with biofuels - there is simply not enough arable land to grow fuel crops and food.
Sunday's flight may herald a new direction in aviation. But any massive change in the way we power our planes is unlikely, analysts say, to be just around the corner.