Editing Korean Air Lines Flight 007 (section)

===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°.<ref name="ICAO93" />{{Rp|31}} 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),<ref name="ICAO93" />{{Rp|41}} to bring it closer to a route known as J501, which KAL 007 was to take to [[Bethel, Alaska|Bethel]]. Approximately 90 seconds later, ATC directed the flight to "proceed direct Bethel when able."<ref name="Luffsey">{{cite web |url=http://testimony.ost.dot.gov/test/pasttest/83test/luffsey1.PDF |date=September 19, 1983 |access-date=February 11, 2009 |title=Statement by Walter F. Luffsey, Associate Administrator for Aviation Standards, Before the House Committee on Science and Technology, Subcommittee on Transportation, Aviation and Weather Concerning Navigation Systems}}</ref><ref>ICAO 1983, appendix C, p. 2.</ref> 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°,<ref name="ICAO93" />{{Rp|31}} roughly toward Bethel.

Upon KAL 007's arrival over Bethel, its flight plan called for it to take the northernmost of five {{convert|50|mi|km|adj=mid|-wide}} [[Airway (aviation)|airways]], known as the NOPAC (North Pacific) routes, that bridge the Alaskan and Japanese coasts. That particular airway, R20 (''[[NATO phonetic alphabet|Romeo]] Two Zero''), passed as close as {{convert|20|mi|km|0}} 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, [[VHF omnidirectional range|VOR/LOC]], [[Instrument landing system|ILS]], and [[Inertial navigation system|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 [[waypoint]]s 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 {{convert|7.5|nmi|km|1}} of that course line.<ref name="ICAO93"/>{{Rp|42}} If, however, the plane was more than {{convert|7.5|nmi|km|1}} 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 {{convert|7.5|nmi|km|1}} 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 {{convert|7.5|nmi|km|1}} 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.<ref name="degani" /><ref name="ICAO93"/>{{Rp|42}}

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.<ref name="degani">{{cite web |url=http://ti.arc.nasa.gov/m/profile/adegani/Crash%20of%20Korean%20Air%20Lines%20Flight%20007.pdf |title=The Crash of Korean Air Lines Flight 007 |access-date=July 4, 2017}}</ref>

The Anchorage [[VHF omnidirectional range|VOR]] beacon was not operational at the time, as it was undergoing maintenance.<ref>Rosenthal, p. 70</ref> 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, {{convert|346|nmi|km|0}} 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.

[[File:KAL007.svg|thumb|A simplified [[CIA]] map showing divergence of planned and actual flight paths]]
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.<ref name="Daniloff, p. 304">Daniloff, p. 304</ref>

[[International Civil Aviation Organization]] (ICAO) [[Flight simulator|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.<ref name="NASA" /><ref>Milde, p. 53</ref> 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 [[Sparrevohn Air Force Station|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 {{convert|7.5|nmi|km|1|adj=on}} 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.<ref name="NASA" />

At 27 minutes after KAL&nbsp;007's take-off, civilian radar at [[Kenai Peninsula|Kenai]], located about {{convert|50|nmi|km|-1}} southwest of Anchorage and with coverage of up to {{convert|175|nmi|km|-1}},<ref name="ICAO93" />{{Rp|10}} showed it passing near Cairn Mountain, about {{convert|160|nmi|km|-1}} west of Anchorage.<ref name="ICAO93" />{{Rp|15}} It also showed that the aircraft by then was already off course—about {{convert|6|nmi|km|0}} north of its expected route to Bethel.<ref name="ICAO93" />{{Rp|4–5, 43}}

Later, at 13:49 UTC (49 minutes after take-off), KAL&nbsp;007 reported that it had reached its Bethel waypoint, about {{convert|346|nmi|km|0}} west of Anchorage.<ref name="ICAO93" />{{Rp|5}} But traces from military radar at [[King Salmon, Alaska]], showed that the aircraft then was actually about {{convert|12|nmi|km|0}} north of that location<ref name="ICAO93" />{{Rp|5, 43}}—and heading farther off course.<ref name="ICAO93" />{{Rp|44}} 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&nbsp;007's deviation and in a position to warn the aircraft.<ref>Pearson, pp. 40-41</ref> 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 {{convert|2|nmi|km|1}} per hour of flight.<ref name="ICAO93" />{{Rp|43}}<ref>Pearson, p. 40</ref>

KAL&nbsp;007's divergence prevented the aircraft from transmitting its position via shorter-range [[very high frequency|very-high-frequency]] radio (VHF). It therefore requested KAL&nbsp;015, also en route to Seoul, to relay reports to air traffic control on its behalf.<ref name="Wyler">{{cite court |url=http://bulk.resource.org/courts.gov/c/F2/928/928.F2d.1167.86-5515.86-5400.86-5524.86-5562.86-5596.html |litigants=Fred Wyler, Individually and as a Personal Representative of the Estate of William Paul Wyler, Deceased, for the Benefit of Himself and Helen C. Wyler, et al., Appellants v Korean Air Lines Company, Ltd., et al. |access-date=February 11, 2009 |date=April 3, 1991 |court=United States Court of Appeals, District of Columbia Circuit}}</ref> KAL&nbsp;007 requested KAL&nbsp;015 to relay its position three times. At 14:43&nbsp;UTC, KAL&nbsp;007 directly transmitted a change of [[estimated time of arrival]] for its next waypoint, NEEVA, to the international [[flight service station]] at Anchorage,<ref>Kleiner, ''Korea, a Century of Change''</ref> 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 [[Noise (radio)|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&nbsp;007 of their ever-increasing divergence<ref name="Pearson">Pearson (1987), p. 40</ref> and was not considered unusual by air traffic controllers.<ref name="Wyler" /> Halfway between Bethel and waypoint NABIE, KAL&nbsp;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&nbsp;007 continued its journey, ever-increasing its deviation—{{convert|60|nmi|km}} off course at waypoint NABIE, {{convert|100|nmi|km}} off course at waypoint NUKKS, and {{convert|160|nmi|km}} off course at waypoint NEEVA—until it reached the [[Kamchatka Peninsula]].<ref name="ICAO93">{{Cite web |date=June 1993 |title=Destruction of Korean Air Lines Boeing 747 on 31 August 1983, Report on the Completion of the ICAO Fact-finding Investigation, June 1993 |url=https://aviation-is.better-than.tv/KAL007%20ICAO%20DESTRUCTION%20OF%20KOREAN%20AIR%20LINES%20BOEING%20747.pdf |access-date=June 14, 2020 |publisher=[[International Civil Aviation Organization]]}}</ref>{{Rp|13}}

{{geoGroup|section=Flight_deviation_from_assigned_route}}

{| class="wikitable" style="text-align:left;"
|-
!Route J501 / R20 waypoint<ref name="ICAO93"/>{{Rp|13}}
!Flight-planned coordinates
![[Air traffic control|ATC]]
!KAL&nbsp;007 deviation
|-
|CAIRN MOUNTAIN
|{{Coord|61|06.0|N|155|33.0|W |type:landmark |name=KAL007 Cairn Mountain NDB}}<ref name="ICAO1983">{{cite journal |title=International Civil Aviation Organization [ICAO]: Action With Regard to the Downing of the Korean Air Lines Aircraft |journal=International Legal Materials |date=July 1984 |volume=23 |issue=4 |page=903 |jstor=20692745 |url=https://www.jstor.org/stable/20692745 |access-date=18 April 2023}}</ref>
|Anchorage
|{{convert|6|nmi|km|abbr=on}}<ref name="ICAO93" />{{Rp|43}}
|-
|BETHEL
|{{Coord|60|47.1|N|161|49.3|W |type:landmark  |name=KAL007 Bethel VORTAC}}<ref name="ICAO1983" />
|Anchorage
|{{convert|12|nmi|km|abbr=on}}<ref name="ICAO93" />{{Rp|43}}
|-
|NABIE
|{{Coord|59|18.0|N|171|45.4|W |type:landmark |name=KAL007 NABIE}}
|Anchorage
|{{convert|60|nmi|km|abbr=on}}
|-
|NUKKS
|{{Coord|57|15.1|N|179|44.3|E |type:landmark |name=KAL007 NUKKS}}<ref name="ICAO1983" />
|Anchorage
|{{convert|100|nmi|km|abbr=on}}
|-
|NEEVA
|{{Coord|54|40.7|N|172|11.8|E |type:landmark |name=KAL007 NEEVA}}
|Anchorage
|{{convert|160|nmi|km|abbr=on}}
|-
|NINNO
|{{Coord|52|21.5|N|165|22.8|E |type:landmark |name=KAL007 NINNO}}
|Anchorage
|
|-
|NIPPI
|{{Coord|49|41.9|N|159|19.3|E |type:landmark |name=KAL007 NIPPI}}
|Anchorage/[[Tokyo Area Control Center|Tokyo]]
|{{convert|180|mi|km|abbr=on}}<ref>Johnson, p. 16</ref>
|-
|NYTIM
|{{Coord|46|11.9|N|153|00.5|E |type:landmark |name=KAL007 NYTIM}}
|Tokyo
|{{convert|500|nmi|km|abbr=on}} to point of impact
|-
|NOKKA
|{{Coord|42|23.3|N|147|28.8|E |type:landmark |name=KAL007 NOKKA}}
|Tokyo
|{{convert|350|nmi|km|abbr=on}} to point of impact
|-
|NOHO
|{{Coord|40|25.0|N|145|00.0|E |type:landmark |name=KAL007 NOHO}}
|Tokyo
|{{convert|390|nmi|km|abbr=on}} to point of impact
|}