By Richard Black
Environment correspondent, BBC News website
Air New Zealand says it plans to mount the first test flight of a commercial airliner partially powered by biofuel.
The 747 flight, scheduled for 2008 or 2009, will not carry passengers
The 747 flight is one part of a deal signed by the airline, engine producer Rolls-Royce and aircraft manufacturer Boeing to research "greener" flying.
One of the four engines will run on a mixture of kerosene and a biofuel, and is set for late 2008 or early 2009.
But Virgin Atlantic is planning to beat Air New Zealand to the punch by having its own biofuel flight early next year.
Air New Zealand's chief executive Rob Fyfe said that advances in technology had made biofuels a viable possibility for use in aviation sooner than anticipated.
The New Zealand government recently declared the objective of becoming carbon neutral, and climate change and energy minister David Parker said the national airline's initiative would help achieve that goal.
"I'm delighted that Air New Zealand has taken the lead by signing up for the first commercial trial of a biofuelled... aircraft," he said.
The partnership gave no details of the type of biofuel to be used, but said that the test flight will not carry passengers.
Race for the skies
Whether Air New Zealand and its partners will achieve a first appears uncertain. Virgin Atlantic is planning a UK-based test flight early next year which would also see one engine of a four-engined commercial jet running partially or entirely on a biofuel.
A Virgin spokesman told the BBC that ground testing was well underway in the US in partnership with GE and Boeing. But this team also has yet to decide which fuel to use.
A spokeswoman for Rolls-Royce said taking to the skies first was not the point.
"It's not particularly a race, that's not the objective," she told BBC News.
"The objective is to gain a better understanding of the potential that biofuels might have for the future."
Once hailed as a clean green saviour, the whole field of biofuels has become more complex and controversial over the last couple of years.
Research shows that some existing technologies actually result in increased greenhouse gas emissions compared with conventional fuels.
There is growing concern too about the amount of land needed to grow existing fuel crops such as rape and maize, and about the impact on wildlife.
"It's become flavour of the month for airlines to talk about biofuels, and flavour of the month for environmentalists to say they're not the answer," observed Tim Johnson, director of the Aviation Envionment Federation, a UK-based research and campaign group.
"And it's not just aviation chasing them, it's every sector; and at the end of the day, can we deliver on the supply side?"
AEF, along with many other observers, is more interested in the potential of so-called second generation biofuels, where entire plants grown specifically for fuel can be processed, rather than just parts of food crops as at present.
This approach would use land more efficiently and produce far higher carbon savings. But the technology is in its infancy, and widespread commercial use probably a decade away.