One week after a frightening near miss between two Japan Airlines jetliners over Yaezu in Shizuoka Prefecture, it seems almost certain that the near midair collision was caused by a combination of human errors. While investigators have yet to reach a conclusion, two human factors — incorrect instructions from air-traffic controllers and confused reactions on the part of the pilots — apparently caused the two planes to come dangerously close to each other last Wednesday in the crowded skies over Shizuoka.

Investigations have found that the planes came within 10 meters of colliding. Forty-two of 427 passengers and crew members aboard the Naha-bound Boeing 747 from Haneda were injured, some seriously, when the plane took a sharp turn and dived to avert a crash. Indeed, it was one of the worst near misses in memory.

Aircraft are equipped with an array of high-tech safety devices to prevent accidents. This incident, however, is a chilling reminder that a simple human error could result in a disaster despite these fail-safe systems. The lesson is clear enough: All safety rules, including air traffic control procedures, should be re-examined thoroughly to secure flying safety.

According to investigators, a couple of control-tower personnel — a male trainee and a female instructor — were keeping track of the two JAL jetliners at the time of the incident. A minute earlier, the man had instructed the jumbo jet to descend, mistaking its flight number 907 for 958, the number of a DC-10 that was heading for Narita from Pusan, South Korea, with 250 passengers and crew members aboard. The instructor also mistook the numbers in communicating with the two flights.

Before the instruction was issued, Flight 907 was ascending while Flight 958 was cruising at about the same altitude. The traffic alert and collision-avoidance system (TCAS) on both planes were activated, signaling 907 to continue ascending and 958 to descend. Then, following the order from the tower, Flight 907 descended while Flight 958, heeding the TCAS warning, also descended.

The narrow escape occurred on the main air route linking eastern and western Japan. With some 420 aircraft flying daily on this route, including those to and from Narita and Haneda international airports, traffic control imposes a heavy load on tower personnel. Not surprisingly, they call the skies over Yaezu a “dangerous area.” Labor unions, among others, complain that the number of controllers has been cut as a result of the introduction of high-tech safety systems such as TCAS.

In order to prevent near collisions, not to mention actual collisions and other accidents, it must first be established exactly what happened. According to reports submitted to transport authorities by the pilots of both aircraft, there was an altitude difference of just 10 meters when the two planes passed by. The pilot of Flight 958 says he first tried to avert a collision as instructed by TCAS, but, seeing another plane coming toward him, stopped descending and headed off a collision on his own initiative.

According to JAL and others, the training controller ordered the ascending 907 to descend. Immediately after that, however, the instructor ordered it to ascend. But it was too late; the plane had already begun its descent. If it had continued to ascend as instructed by TCAS, 907 would have flown at a safe altitude above 958. It is clear, as revealed by the investigations, that the male controller gave the wrong order by mixing up the flight numbers. Although the air traffic control procedures are already being reviewed, there must be a thorough investigation.

Beyond that, it is doubtful whether a trainee should be used the way he was, even in the presence of an instructor. It is not that on-the-job training in a congested area is unnecessary. The training itself needs to be improved, certainly. The question is how to train. Assigning just one instructor to an area crowded with large passenger planes may not be enough.

This is not the first time a near collision has occurred. Last December, in a part of the same air zone, over Izu Oshima Island, JAL planes also came within a whisker of a crash, touching off an anticollision alarm. This time, although a disaster was averted, more than 40 people were injured. Responsibility for this, not just for the fact of the near miss, must be sought.

JAL, of course, needs to step up efforts to secure flying safety and improve pilots’ skills in crisis avoidance. Air traffic control authorities, meanwhile, must see to it that control procedures are followed correctly in all situations. At the same time, they should conduct a wholesale review of the safety rules, including methods of training.

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