Instead, Indian authorities fingered the Kazakh pilots and their equipment. The aviators from the former Soviet republic, they said, did not understand English instructions clearly, flew badly maintained aircraft and had been involved in near collisions in the past. And "KazAir," they added, is the worst of the national airlines formed when the Central Asian republics gained independence. Kazakhstan authorities closed the airline down a few months ago because of safety considerations. It was restarted after a local bank took over its administration.

But the vice-president of KazAir, Ildus Nazmutdinov, defended his airline. The plane involved in the accident was in good technical condition, he said. "Our pilot knew English. We're just starting the investigation and have very few details." The transcript of the controller's conversation suggested that the Kazakh pilot did, in fact, understand the instructions. Indian officials, however, believe he might have failed to recalculate the altitude into feet. But KazAir officials insist the aircraft had altimeters in feet as well as meters.

The location of the debris led to speculation that the Saudi pilot might have misinterpreted the controller's instructions and climbed higher than the 14,000 he had been cleared for. One of the plane's engines was found on top of the Ilyushin's tail -- a possible indicator of the point of impact. The juxtaposition also suggested that the Boeing had been flying higher than the Kazakh plane at the time of collision. The cockpit instruments show that impact occurred at 14,800 feet, which means the Ilyushin was some 200 feet below its prescribed height and the Boeing 800 feet above it.

The one-week-old investigation is uncovering shortcomings at India's busiest airport. The radar at Delhi is an older model that gives readings in only one dimension -- range. More modern systems indicate the height, speed and direction of aircraft, giving controllers a three-dimensional picture of the traffic. Although the controller involved had told the planes to fly at different heights, his equipment could not verify whether they were actually keeping to the prescribed limits. He could only watch as the two blips on his screen hurtled toward each other at a combined speed of 800 miles an hour, hoping they would pass each other safely.

A newer radar, purchased from the American Raytheon Corp. for $128 million, had been installed. But, say government sources, it was not working -- even though it should have been by October last year. New Delhi has ordered another investigation to find out why. The Air Traffic Controllers' Guild says that it urged authorities a month ago to upgrade the capital's systems.

Some aviation experts have questioned the wisdom of allowing the aircraft to pass directly over and under each other within New Delhi's 40-km commercial air corridor. They advocate horizontal separation. Because of security considerations, the capital has only a single corridor for incoming and outgoing flights that is oriented east and west -- the general direction of Pakistan. The Indian Commercial Pilots Association says it alerted the government to this danger more than a year ago. At the same time, air traffic has ballooned from 68,000 flights in 1993 to 168,000 this year because of India's new open-skies policy. Near misses have become a frequent occurrence.

Neither aircraft was fitted with automatic airborne advisory systems that would have warned pilots they were on a collision course. The Saudi Boeing was an older model which did not have the device, and the Russian-made Ilyushin was not equipped with them. And for the systems to work, the planes would have had to be fitted with compatible models. In the United States, all aircraft are required to be so outfitted, and the same rules will be in force in Europe by 2000.