When an airplane hits another airplane in flight, there are no survivors. This axiom of aeronautic safety has been demonstrated most graphically twice in the past two years: first when 128 people were killed in a collision over the Grand Canyon in June, 1956, and then last month, when an airliner and a jet trainer collided over the Nevada desert.

Both these incidents point to a serious problem confronting the aviation industry--safe, effective control of air traffic. The present system, geared to handle out-moded DC-3's, is obviously inadequate, and, as planes become faster and more numerous, the situation grows worse.

A pilot needs at least three seconds to see and react to an approaching plane; with both planes flying at 300 miles per hour (considerably slower than the speed of the jet airliners which will enter service this winter), three seconds means half a mile. In other words, by the time a pilot can adjust his course to avoid another plane, the other plane is upon him. In addition, the controls of a modern airplane are so complicated as to require a pilot's almost undivided attention. He does not have time to watch for other planes, and when he does, his field of vision is necessarily limited by the dimensions and position of his cockpit.

Commercial airliners, the Airline Pilots Association has disclosed, are involved in an average of four near-collisions every day, and in one quarter of these the planes pass within 100 feet of each other. From 1950 till the Grand Canyon disaster on June 30, 1956, almost seventy collisions involving civil airplanes took place(not including a high military total), but none had previously involved passenger planes. Many experts consider it possible, even likely, that a collision might occur over a large city, where the worst traffic jams are located.

The case history of the Grand Canyon disaster indicates some of the shortcomings of the present traffic control system. The two planes--a Trans-World Airlines Super-Constellation and a United Airlines DC-7--took off from Los Angeles three minutes apart and were to fly approximately the same course. The TWA plane, flying at 17,000 feet, ran into a thunderstorm and requested permission from a Civil Aeronautics Administration station, to climb to 21,000 feet; the request was turned down because the UAL plane already occupied that altitude. The TWA pilot then asked to fly 1000 feet "above the weather"--a normal request that was granted.

This action meant that the pilot was "on his own,"and was responsible for avoiding any other planes that might be in the area. Investigators assume that the TWA plane, climbing to avoid the bad weather, came up underneath the DC-7 and hit it. Neither pilot, had he seen what was happening, would have been able to adjust course in time to avert the accident.

Both pilots in the Grand Canyon incident were on "visual flight rules," and not assigned to a definite airway, because Arizona and most of the Southwest are classified as "free air," and are not completely controlled by the CAA.

But this collision, and the others that occurred before and after it, have demonstrated that a more reliable safeguard that the human nervous system is needed. The CAA tracking system relies on manual posting of each plane's position on a map, and cannot possibly control all flights. In addition, military planes operate under a separate, more stringent control system, and the lack of co-ordination between civil and military aviation can result in such collisions as the one in Nevada last month.

C. J. Lawen, director of the CAA, says that "the greatest single problem we face is air traffic control." The CAA's inability to cope with the situation is not entirely its own fault. Its requests for appropriations are consistently halved by the Commerce Department and the Bureau of the Budget. In 1956, the agency began a five-year, $246 million development program which may produce some good results.

The most promising solution to the air traffic problem, however, probably lies in SAGE (Semi-Automatic Ground Environment), the air defense radar network being constructed by the Defense Department at a cost of $3 billion. When it is completed, this system reportedly will be able to detect, identify and track all aircraft over the United States. If the CAA can somehow, through cooperation with the SAGE system, place its tracking operations on a semi-automatic basis, a method of effective traffic control will become possible, and the risky "visual flight" operation may be all but eliminated.

Statistics show that air travel, on the whole, is a safe business. But each collision (and there are quite a few, involving military or non-passenger planes, that do not receive wide publicity) indicates that aviation is still not as safe as it might be. The situation will become even more dangerous with the advent of widespread jet traffic, a phenomenon for which American aviation is singularly unprepared.