AP reports that Air NZ has successfully trialled flying a 747 using a 50% mix of jatropha oil - NZ airline flies jetliner partly run on veggie oil.

A passenger jet powered in part by vegetable oil successfully completed a two-hour flight Tuesday to test a biofuel that could lower airplane emissions and cut costs, Air New Zealand said. One engine of a Boeing 747-400 airplane was powered by a 50-50 blend of oil from jatropha plants and standard A1 jet fuel.

This year has seen an unprecedented push for alternative fuels by airlines, which were slammed by skyrocketing oil prices earlier in 2008 and are now bracing for a falloff in air travel in the face of a global economic slowdown.

While Air New Zealand couldn't say whether the blend would be cheaper than standard jet fuel since jatropha is not yet produced on a commercial scale, the company expects the blend to be "cost competitive," according to company spokeswoman Tracy Mills.

Biofuels were once regarded as impractical for aviation because most freeze at the low temperatures encountered at cruising altitudes. But tests show jatropha, whose seeds yield an oil already used to produce fuels like biodiesel, has an even lower freezing point than jet fuel.

Air New Zealand Chief Executive Rob Fyfe called the flight "a milestone for the airline and commercial aviation." "Today we stand at the earliest stages of sustainable fuel development and an important moment in aviation history," he said shortly after the flight. The company's goal is to become the world's most environmentally sustainable airline.

The flight was the first to use jatropha as part of a biofuel mix.

In February, Boeing and Virgin Atlantic carried out a similar test flight that included a biofuel mixture of palm and coconut oil — but was dismissed as a publicity stunt by environmentalists who said the fuel could not be produced in the quantities needed for commercial aviation use.

Biofuels emit as much carbon as kerosene-based jet fuel, but jatropha — a Mexican plant that grows in warm climates — absorbs about half the carbon that jatropha-based fuels release. Air New Zealand's proposed blend, for example, would mean a one-quarter reduction in the carbon footprint of standard jet fuel.

Many biofuels — like ethanol, which is produced from corn — have been blamed for raising the price of food by diverting it from kitchen tables to engines. While the link between biofuels and grain prices is debatable, Mills said that jatropha plants would not compete with food or other commercial crops since it can grow on land that would make poor farmland and needs little water.

"Ethanol is a first generation biofuel; jatropha a second generation biofuel that doesn't compete for land with food production," Mills said.

The test flight out of Auckland International Airport included a full-power takeoff and cruising to 35,000 feet (10,600 meters), where the crew manually set all four engine controls to check for identical performance readings among the biofuel-powered engine and those using jet fuel. Pilots also switched off the fuel pump for the biofuel engine at 25,000 feet (7,600 meters) "to test the lubricity of the fuel," ensuring its friction in the pipe did not slow its flow to the engine.

The Australian reports that Air New Zealand will soon trial a fuel mix using 50% biofuel from jatropha plants - Oil from wasteland tree to power Air NZ jet.

A BIOFUEL due to be used in a world-first Air New Zealand flight test next month may give aircraft an energy boost and reduce their environmental footprint.

Tests by engine-maker Rolls Royce show the 50/50 blend of Jet A1 and fuel converted from jatropha plant oil met or exceeded all critical criteria, including a freeze point of -47C and flash point of 38C. But it also has a higher energy content and lower specific gravity than the Jet A1 fuel available in most countries and the Jet A fuel airlines buy in the US.

Rolls-Royce, which tested the fuel at facilities in Britain, said the blend met or exceeded technical requirements for civil and military aircraft as well as the requirements of a "drop-in" fuel whose properties were virtually indistinguishable from conventional fuel. This means it can be put straight into today's jet engines without the need to make expensive modifications.

Air NZ chief pilot David Morgan said the ability to mix the biofuel with normal fuel was important because airlines may not be able to get the new type in all ports. He expected airlines to be able to use anything from 100 per cent biofuel to various levels of blends.

He also expected to see a reduced fuel burn per nautical mile because of the higher energy content in the new is fuel. He noted that Qantas and Air NZ flights buying the less energy-rich Jet A in the US loaded a 0.2 to 0.3 of a per cent extra because it had less calorific value. This meant, all things being equal, that airlines used more fuel coming out of the US than in travelling there. "So the high calorific value and low specific gravity is a win-win," he said.

Mr Morgan said the aviation industry consortium involved in the test had opted for a blend was because of the biofuel's lower specific gravity. "For the purpose of the test we need to bring it close to normal jet fuel specific gravity because one of the purposes of this test is to prove the efficacy and viability of biofuel in the normal system," he said.

Air NZ will test the blend in various operating conditions in one of the four RB211 on the 747 during a two-hour flight on December 3 and Mr Morgan doe not anticipate any surprises.