Korean Air Lines[?] KE007 was a commercial Boeing 747 flying from New York, USA to Seoul, Korea. It took off from New York's John F. Kennedy International on August 31 carrying 246 passengers and 23 crew. After refueling at Anchorage, Alaska the aircraft took off, flying southwards for Seoul-Kimpo airport but at a course (245 degrees) that would take the craft much further westwards than usual, cutting across the Kamchatka peninsula and then over the Sea of Okhotsk towards Sakhalin.
As the aircraft approached and then overflew Soviet territory, Su-15[?] and MiG-23 fighters were scrambled. Two Sukhoi Su-15s from Dolinsk-Sokol airbase intercepted and shot down the airliner with a single missile attack at 18.26 local time. The airliner crashed into the sea about 55 km off Moneron Island killing all on board. Initial reports that the airliner had been forced to land on Sakhalin were soon proved false. CVR (cockpit voice recorder) transcripts recovered from the airliner show the crew undertaking an emergency spiral descent due to rapid decompression from 18.26 until the end of the recording at 18.27:46.
Ronald Reagan condemned the shooting down on September 5, calling it the "Korean airline massacre", a "crime against humanity [that] must never be forgotten" and a "act of barbarism... [of] inhuman brutality". The attack was used by the United States government to pull relations with the Soviet Union to a new low.
An International Civil Aviation Organization investigation concluded that the course taken was accidental: a result of the autopilot being either left in heading mode or having been switched to INS when outside of the range for the INS to capture the correct track. This left the airliner proceeding on the constant magnetic heading chosen when the craft left Anchorage. The crew did not notice this error or undertake the correct INS checks to discover it later due to a "lack of situational awareness and flight deck co-ordination". It is believed that the airliner was briefly on a matching course close to a USAF RC-135[?] northeast of Kamchatka and as the aircraft diverged the Soviet radar tracked one signal heading away and one coming dangerously close.
It was known that the USSR could attack without warning overflights of the area but the confusion and the non-compliance with standards for interception reflects poorly on the Russian military.
As with any serious disaster a number of conspiracy theories have arisen. The theorists main concerns are why the airliner was off course and even whether it did crash.
The most interesting 'off course' theory is that the flight was part of a deliberate US intelligence gathering effort. The theories claiming KAL-007 did not crash relate to a number of issues. It is claimed to be unlikely that a single missile would knock a 747 out of the air, the loss of a single engine is not catastrophic for such a craft. Reports of the crash put the time from missile strike to sea impact at around twelve minutes, which is high for an uncontrolled descent. The crew aboard the airliner never announced a mayday despite there being two further communications from the 747. The amount of material recovered from the accident compares unfavourably with other crashes of roughly equal magnitude as does the type of material retrieved. That only two bodies were recovered, relatively intact, is also surprisingly low. All searches, either by the Soviets, Japanese or Americans were ended in early November, 1983.
The 'no crash' theorists do not go to explain why the plane was off-course, or why the Soviets would want to hold onto 260 or so airline pasengers, except through the far-fetched claim that they were targetting a single passenger and felt it was necessary to keep all of the other people in captivity to conceal this.