The Pearl River Delta is serviced by five airports - Hong Kong, Guangzhou, Macau, Zhuhai and Shenzhen - each with their own airspace procedures. Pilots approaching from the north must navigate through each airspace before landing at Hong Kong's International Airport, which means extra flight time - and more fuel being burned. Captain Russell Davie, airline operations manager for Cathay Pacific, says these restrictions result in an extra 25,000 tonnes of fuel burned each year by Cathay flights alone. Giovanni Bisignani, director-general of the International Air Transport Association (Iata), priced the inefficiency at US$400 million, reported earlier by trade magazine Orient Aviation. 'This unnecessary cost to airlines and the environment is not acceptable. Iata is working closely with all parties to rationalise the situation.' Given the high altitude at which jet fuel burns and its relatively high quality, the impact of this inefficiency on Hong Kong's air pollution is tenuous at best. The carbon dioxide emitted as a result, however, does have implications on global warming. There is also increasing attention paid to the pollution that shipping generates, given 172,080 vessels arrived in the city in the first nine months of last year. Under present international regulations, the sulphur content of bunker fuel could be as high as 4.5 per cent. Hong Kong's diesel for road vehicles has a sulphur content of 0.005 per cent. Government statistics for 2003 showed 'navigation' accounted for just 4 per cent of sulphur dioxide emissions and 15.7 per cent of nitrogen oxide emissions. But environmental groups say the toxic fumes are emitted close to ground level, and pollutants blow directly into heavily populated areas.