The Hong Kong Civil Aviation Department is studying ways to maximize airspace use to increase the number of flights into and out of Hong Kong.

Civil Aviation director-general Norman Lo Shung-man said on August 22 that one possible measure would be to reduce the distance between planes from the current six nautical miles (about 11 kilometers) for a light plane following a heavy plane, and five miles (9km) for a medium plane following a heavy plane, to just four miles (7.4km), which is the standard for two heavy planes following one and another.

He said the department was looking at such factors as air currents that may be caused by the shortened distance, and other safety factors.

"Safety remains our first priority before any new requirement can be set," Lo said during a press tour of Hong Kong International Airport.

He said that in November China will follow the Hong Kong model of a minimum flight altitude of 1,000 feet (304 meters) between two planes flying below 40,000 feet.

Lo said if the four-mile limit was adopted, it would effectively save 482,144 miles or about 1,800 flight hours per year, translating to between five and seven minutes for each flight.

He said that since, for safety reasons, independent parallel operations were out of the question on Hong Kong's parallel runways, it was necessary to find other ways to maximize capacity.

Lo said a study on the necessity of constructing a third runway was expected to be completed by the first quarter of 2008, though it would take a further year or two before a feasibility report is made. A few more years would be required for its construction.

"It is not for a CAD director to say whether a third runway is necessary for Hong Kong. But if there is a demand for more flights, and if this will result in a positive economic impact, then it sounds like a good idea, " he said.

"However, we have to tackle many obstacles, such as the mountain barrier and environmental issues. If we do not conduct the feasibility study now, we will be wasting about 10 years."

Lo said reclamation would be needed to build a new runway.

Runway capacity now is about 54 flights per hour for the two runways. The CAD expects it will be increased to 55 flights per hour this winter and then progressively increased to 58 by 2009. "We had 65 flights before and it is possible to reach 70. But it would be difficult to further increase the capacity under the current system," Lo said.