THE DIRECTION of the investigation into the fatal crash of EgyptAir Flight 990 should be guided by the evidence and not by diplomatic or political considerations. It is necessary to say this in light of the National Transportation Safety Board's (NTSB) decision to retain jurisdiction over the inquiry after the Egyptian government objected to an FBI-led criminal probe.

Safety board chairman Jim Hall says his decision to put off the FBI until Egypt's own experts can examine the voice and flight data recorder tapes was driven by a "prudent" desire to consult with Egyptian officials and experts before the matter is turned over to the FBI. But it may also delay getting at what caused that horrific crash. Mr. Hall has already said that evidence collected thus far indicates that no mechanical or weather-related problems could have caused it.

NTSB officials had planned to turn the probe over to the FBI after they heard on the plane's voice recorder what they think is one of the pilots, apparently alone, uttering a prayer in Arabic before turning off the auto-pilot and forcing the jet into a high speed dive. Unless there is evidence offering a convincing alternative explanation of that person's actions, the NTSB should not be deterred from pursuing its original course.

A more thorough investigation and analysis, whether conducted by the NTSB or by the FBI, could well lead to the conclusion that the plane was not deliberately crashed. Perhaps some mechanical problem will be detected. That would lift the looming criminal cloud so feared by Egyptian authorities.

But the Egyptian claim that the safety board has misread the evidence and is rushing to judgment must be based on more than distaste for a criminal probe. The objections need to be bolstered by supporting facts, not diplomatic entreaties. The overriding concern of the authorities, whether American or Egyptian, must be to find out what happened, including whether the crash was an accident or a deliberate and maniacal act.