SUDDENLY an incident that looks at first glance like a stunt -- the young West German pilot's landing of a civilian plane in Red Square -- becomes a major political event in Mikhail Gorbachev's Kremlin. The defense minister and the air defense commander are out on their ears in what has to be seen both as a major shake-up and as a recalibration of one of the most sensitive political connections in a communist society, the relationship between the ruling Communist Party and the military command.

If it wasn't some sort of rigged event we don't know about, 19-year-old Mathias Rust's daring solo flight in a little Cessna 172 across more than 400 miles of heavily guarded Soviet territory was the most audacious violation yet known of Soviet air space -- and of Soviet pride. He landed hard by the Kremlin, the very symbol of the Soviet fortress, and this in a country that puts an immense premium on air defense. But this was not the first intrusion. In 1978 and again in 1983 South Korean airliners wandered deep into Soviet air space. The first plane was eventually forced down, and the second was shot down with the loss of 269 lives. So the Soviet military was surely on notice when the Cessna was observed on Thursday after taking off from Helsinki. Yet Soviet fighter planes merely circled it and let it proceed without interference on what turned out to be its way to Moscow.

It is just possible that the restless, modernizing Mr. Gorbachev, keen to the uses of power, had been wishing for such an occasion to move out the old-guard defense minister, Marshall Sergei Sokolov, 75, whom he inherited when he became party general secretary two years ago. In any event, the incident let him make a personnel shift that can be explained in terms of defense requirements and Soviet internal politics. That is what was indicated by an unusual Politburo statement that not only announced the personnel shifts but also delivered a rare institutional critique: "Serious shortcomings in organizing the protection of the air space of the country, a lack of due vigilance and discipline and major dereliction of duty in the guidance of forces by the U.S.S.R. Defense Ministry." Clearly, the military has been taken down a large peg.

But if that's clear, not much else is, which should warn off those who are tempted to use this incident for making points or drawing lessons about such things as accountability, the effectiveness of Soviet defenses and the implications of it all for U.S. strategy. Before we get into that heavy stuff, it would be good to know something more about the motives and machinations behind the bizarre and mysterious flight of Mathias Rust