The Ministry of Land, Infrastructure and Transport plans to more than halve the minimum separation distance between commercial aircraft flying over the busy North Pacific and polar route between Japan and the U.S. East Coast.

The measure, likely to be enforced in 2004 with the use of a new satellite-based global positioning system, would cut the minimum distance two aircraft must maintain from each other from the current 220 km to about 90 km.

The new flight control system, based on the Multifunctional Transport Satellite the transport ministry plans to launch this summer, will allow air controllers to double the volume of traffic over the North Pacific, create more room on flight routes and cut departure and arrival delays.

Under the existing system, controllers keep track of airplanes by radio as the airspace above the Pacific cannot be monitored by radar. The MTSAT can automatically send aircraft position data through the onboard GPS.

The new system may also improve aircraft energy efficiency, officials said.

Pilots of jetliners flying over the North Pacific typically want to operate at optimum energy-efficient altitudes by tapping the jet stream. Under current regulations, however, 35 percent of the planes are not allowed to fly at their desired altitudes.

The transport ministry also hopes the new system will reduce glitches inherent in radio communications, which can be hampered by distance and weather conditions.

Digitally transmitted information from the MTSAT would provide accurate communications with clear audio and text data, ministry officials said.