Korean Air Lines Flight 007

Korean Air Lines Flight 007 was a scheduled Korean Air Lines flight from New York City to Seoul via Anchorage. On September 1, 1983, the flight was shot down by a Soviet Sukhoi Su-15 interceptor aircraft. The Boeing 747-230B airliner was en route from Anchorage to Seoul, but owing to a navigational mistake made by the crew, the airliner drifted from its planned route and flew through Soviet airspace. The Soviet Air Forces treated the unidentified aircraft as an intruding U.S. spy plane, and destroyed it with air-to-air missiles, after firing warning shots. The South Korean airliner eventually crashed into the sea near Moneron Island west of Sakhalin in the Sea of Japan, killing all 246 passengers and 23 crew aboard, including Larry McDonald, a United States representative. It is the worst Korean Air disaster to date.

The Soviet Union initially denied knowledge of the incident, but later admitted to shooting down the aircraft, claiming that it was on a MASINT spy mission. The Politburo of the Communist Party of the Soviet Union said it was a deliberate provocation by the United States to probe the Soviet Union's military preparedness, or even to provoke a war. The U.S. accused the Soviet Union of obstructing search and rescue operations. The Soviet Armed Forces suppressed evidence sought by the International Civil Aviation Organization (ICAO) investigation, such as the flight recorders, which were released in 1992, after the dissolution of the Soviet Union.

As a result of the incident, the United States altered tracking procedures for aircraft departing from Alaska, and President Ronald Reagan issued a directive making American satellite-based radio navigation Global Positioning System freely available for civilian use, once it was sufficiently developed, as a common good.

Flight deviation from assigned route

Less than a half-minute after taking off from Anchorage, KAL 007 was directed by air traffic control (ATC) to turn to a magnetic heading of 220°. This sharp turn, 100° to the left, was only to transition the plane from its initial heading at take-off (320° magnetic, in line with the runway it used), to bring it closer to a route known as J501, which KAL 007 was to take to Bethel. Approximately 90 seconds later, ATC directed the flight to "proceed direct Bethel when able." In response, the plane immediately began a slight turn to the right, to align it with route J501, and less than a minute later (3 minutes after take-off) was on a magnetic heading of approximately 245°, roughly toward Bethel.

Upon KAL 007's arrival over Bethel, its flight plan called for it to take the northernmost of five 80 km airways, known as the NOPAC (North Pacific) routes, that bridge the American and Japanese coasts. That particular airway, R20 (Romeo Two Zero), passes within 20 mi from what was then Soviet airspace off the coast of the Kamchatka Peninsula.

The lateral navigation half of the autopilot system of the 747-200 has four basic control modes: HEADING, VOR/LOC, ILS, and INS. The HEADING mode maintained a constant magnetic course selected by the pilot. The VOR/LOC mode maintained the plane on a specific course, transmitted from a VOR (VHF omnidirectional range, a type of short-range radio signal transmitted from ground beacons) or Localizer (LOC) beacon selected by the pilot. The ILS (instrument landing system) mode caused the plane to track both vertical and lateral course beacons, which led to a specific runway selected by the pilot. The INS (inertial navigation system) mode maintained the plane on lateral course lines between selected flight plan waypoints programmed into the INS computer.

When the INS navigation systems were properly programmed with the filed flight plan waypoints, the pilot could turn the autopilot mode selector switch to the INS position and the plane would then automatically track the programmed INS course line, provided the plane was headed in the proper direction and within 7.5 nmi of that course line. If, however, the plane was more than 7.5 nmi from the flight-planned course line when the pilot turned the autopilot mode selector from HEADING to INS, the plane would continue to track the heading selected in HEADING mode as long as the actual position of the plane was more than 7.5 nmi from the programmed INS course line. The autopilot computer software commanded the INS mode to remain in the "armed" condition until the plane had moved to a position less than 7.5 nmi from the desired course line. Once that happened, the INS mode would change from "armed" to "capture" and the plane would track the flight-planned course from then on.

The HEADING mode of the autopilot would normally be engaged sometime after takeoff to follow vectors from ATC, and then after receiving appropriate ATC clearance, to guide the plane to intercept the desired INS course line.

The Anchorage VOR beacon was not operational at the time, as it was undergoing maintenance. The crew received a NOTAM (Notice to Airmen) of this fact, which was not seen as a problem, as the captain could still check his position at the next VORTAC beacon at Bethel, 346 nmi away. The aircraft was required to maintain the assigned heading of 220 degrees until it could receive the signals from Bethel, then it could fly direct to Bethel, as instructed by ATC, by centering the VOR "to" course deviation indicator (CDI) and then engaging the autopilot in the VOR/LOC mode. Then, when over the Bethel beacon, the flight could start using INS mode to follow the waypoints that make up route Romeo-20 around the coast of the U.S.S.R. to Seoul. The INS mode was necessary for this route since after Bethel the plane would be mostly out of range from VOR stations.

At about 10 minutes after take-off, flying on a heading of 245 degrees, KAL 007 began to deviate to the right (north) of its assigned route to Bethel and continued to fly on this constant heading for the next five and a half hours.

International Civil Aviation Organization (ICAO) simulation and analysis of the flight data recorder determined that this deviation was probably caused by the aircraft's autopilot system operating in HEADING mode, after the point that it should have been switched to the INS mode. According to the ICAO, the autopilot was not operating in the INS mode either because the crew did not switch the autopilot to the INS mode (as they should have shortly after Cairn Mountain), or they did select the INS mode, but the computer did not transition from "armed" to "capture" condition because the aircraft had already deviated off track by more than the 7.5 nmi tolerance permitted by the inertial navigation computer. Whatever the reason, the autopilot remained in HEADING mode, and the problem was not detected by the crew.

At 27 minutes after KAL 007's take-off, civilian radar at Kenai, located about 50 nmi southwest of Anchorage and with coverage of up to 175 nmi, showed it passing near Cairn Mountain, about 160 nmi west of Anchorage. It also showed that the aircraft by then was already off course—about 6 nmi north of its expected route to Bethel.

Later, at 13:49 UTC (49 minutes after take-off), KAL 007 reported that it had reached its Bethel waypoint, about 346 nmi west of Anchorage. But traces from military radar at King Salmon, United States, showed that the aircraft then was actually about 12 nmi north of that location—and heading farther off course. There is no evidence to indicate that anyone with access to King Salmon radar output that night—civil air traffic controllers or military radar personnel—was aware in real-time of KAL 007's deviation and in a position to warn the aircraft. But had the aircraft been steered under INS control, as was intended, such an error would have been far greater than the INS's nominal navigational accuracy of less than 2 nmi per hour of flight.

KAL 007's divergence prevented the aircraft from transmitting its position via shorter-range very-high-frequency radio (VHF). It therefore requested KAL 015, also en route to Seoul, to relay reports to air traffic control on its behalf. KAL 007 requested KAL 015 to relay its position three times. At 14:43 UTC, KAL 007 directly transmitted a change of estimated time of arrival for its next waypoint, NEEVA, to the international flight service station at Anchorage, but it did so over the longer range high frequency radio (HF) rather than VHF. HF transmissions can typically be heard at a greater distance than VHF, but are vulnerable to electromagnetic interference and static; VHF is clearer with less interference and is preferred by flight crews. The inability to establish direct radio communications via VHF did not alert the pilots of KAL 007 of their ever-increasing divergence and was not considered unusual by air traffic controllers. Halfway between Bethel and waypoint NABIE, KAL 007 passed through the southern portion of the North American Aerospace Defense Command buffer zone. This zone is north of Romeo 20 and off-limits to civilian aircraft.

Sometime after leaving American territorial waters, KAL Flight 007 crossed the International Date Line, where the local date shifted from August 31, 1983, to September 1, 1983.

KAL 007 continued its journey, ever-increasing its deviation—60 nmi off course at waypoint NABIE, 100 nmi off course at waypoint NUKKS, and 160 nmi off course at waypoint NEEVA—until it reached the Kamchatka Peninsula.