ONE OF the great unsolved mysteries in the history of civil aviation was written on September 1, 1983, when Korean Air Lines Flight 007, more than 300 miles off course, was shot down by a Soviet fighter over Soviet territory.

The incident has fascinated writers and foreign policy specialists alike, partly because the central question is currently unanswerable and possibly always will be, but also because the shoot-down is the most dramatic recent unpleasant incident involving the United States and Soviet Union at a time when they have the ability to incinerate each other and the world. Whatever pre-election chances there were for improving Soviet- U.S. relations went down with the plane.

That central question is: How did the airplane -- a Boeing 747 jumbo -- come to be so far off course? Twice, on a regularly scheduled flight from New York to Seoul after a stop in Anchorage, it penetrated Soviet airspace as it drifted steadily north of its assigned route. The second time the Soviets destroyed it.

For most of its flight the plane was out of range of either United States or Japanese civil radar surveillance -- a normal circumstance on that route -- but the crew members radioed the required progress reports, so there was nothing to alarm the civil alert system.

Various theories have been forwarded to explain what became a massive course deviation, including hijacking, crew incapacitation, mechanical failure, human error in employing the computerized navigation system and the possibility that the plane was on some kind of intelligence mission, presumably sponsored by the United States.

There is enough available information to reasonably exclude hijacking, crew incapacitation and massive mechanical failure. That leaves human error/computer failure or some kind of espionage activity. These two books bring to the discussion a choice between Dallin's careful, responsible and well- reasoned analysis of the issues and possible answers and Clubb's U.S.-bashing political, polemical conspiracy theory.

Dallin presents and analyzes facts in a compelling and eminently readable way; Clubb presents his own conclusions as if they were irrefutably supported by his selective use of facts from what is at best an incomplete record. Dallin is a respected Soviet scholar. After years at Columbia he is now a professor of history and political science at Stanford. Clubb is an associate professor of political science at Syracuse.

Both authors have trouble, in the final analysis, accepting the human/computer failure theory. Both note the earlier Korean Air Lines excursion over Soviet territory -- the Boeing 707 that strayed 1,000 miles off course before being forced down on a frozen lake near Murmansk. "Common sense tells us," Clubb writes, "that routine, highly reliable procedures would have been designed to insure that the INS (inertial navigation system on the plane) is programmed correctly." He concludes that "Logically, U.S. intelligence authorities failed to warn Flight 007 for the same, entirely evident reason they had not warned the KAL airliner which overflew Murmansk five years earlier -- because both flights had been on missions for the National Security Agency."

DALLIN too has trouble swallowing the misprogramming theory and also notes the "strange coincidence" that both recent civil overflights of the Soviet Union have involved South Korean planes. However, he writes, "There is no way for us to push the argument further: it might have been a coincidence, and then again it might have been something else." Flight 007 needed no special equipment, no cameras or recording devices, to do what it undoubtedly did, which was provide an electronic intelligence bonanza for U.S. ears in the Far East. But Dallin cannot bring himself to make the categorical statement that the bonanza was the result of a plan. "This possibility must not be ruled out simply because of the political embarrassment which its validation would occasion," he writes. "In fact, it must be acknowledged that with the passage of time this argument, unlike all others, looms stronger than before."

I have less trouble accepting the misprogrammed computer theory -- not because I think the United States simply would not launch such a risky intelligence mission but because I have covered civil aviation safety for 10 years, have studied dozens of accident reports and know for a certainty that experienced, well-trained, highly qualified flight crews can commit incredible stupidities for unfathomable reasons. However, I have been bothered from the first by a seeming contradiction between what the U.S. military intelligence network obviously knows about the flight-track and communications of Flight 007 and the total absence of warning to the crew from U.S. or Japanese sources. The U.S. explanations are that much of the information was retrieved from recordings after the fact: that there was no real-time monitoring of the flight and therefore no warning to be given even if it were standard practice for military intelligence to warn civilian aircraft, which it is not.

Dallin's book is particularly helpful in understanding the state of U.S.-Soviet relations and the two countries' reactions after the incident. As for Clubb, he wants a full-bore congressional investigation. He sees the flight as another in a long pattern of events apparently designed by sinister forces to thwart meaningful opportunities for real peace.

Doas B. Feaver, a reporter on the national staff of The Washington Post, has covered aviation for several years.