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This question relates to the Flight Management System of a large airliner, e.g. Boeing 787:

During a flight, when the aircraft passes a waypoint, is this just passed waypoint (and the previous ones) still shown on the legs / FPLN page of the Flight Management System? Asked differently, can I scroll through all the past waypoints or are they automatically deleted once I have passed them?

Does the same apply to the Navigation Display (if I'd zoom out enough), would I still see all already sequenced waypoints and the past route, or do I only get to see the upcoming route and waypoints?

If they are not visible any more, why so?

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Previous waypoints are not shown on the 787's CDU. However, they are shown on the map as @skipper44's answer shows. Other planes handle it differently.

The 787 EFB does not show the plane position. Only very recently the FAA allowed own-ship display on moving maps.

As to why, there is no use for it. The POS REPORT page on the 787 would show the three waypoints needed for position reports (from, to, and next).

Some airways are one-way, so it's not like a U-turn will be needed (there is also no reverse sequence function). Any emergency gets priority and a direct-to the nearest suitable airport (weather and terrain permitting).

If the whole plan is needed (on display) for some reason, it can be reloaded as a secondary inactive route (if saved, or if can be requested via uplink).

On the MD-11, the progress page shows the last waypoint (singular), but not the 787, so minor differences can be expected. Above applies to the 787's route legs and progress pages.

Source: 787 FCOM.

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  • $\begingroup$ B737 and A320 FMS are the same. First line of the Legs page is the From waypoint (last leg). Previous legs are not retrievable. $\endgroup$
    – Gerry
    Jan 15, 2018 at 17:54
  • $\begingroup$ Already overflown waypoints of the Active Route on the B787 can be seen to the extent of half of the maximum selectable range using Map Centre mode on the ND. Also to some extent on the Mini-Map display at the bottom of the PFD. $\endgroup$
    – skipper44
    Sep 3, 2021 at 21:41
  • $\begingroup$ @skipper44: Interesting. Does that apply only when LNAV is used? For instance previous waypoints cannot be seen here for example. And what if LNAV was returned to after some vectoring and some planned points were not overflown? $\endgroup$
    – user14897
    Sep 4, 2021 at 16:36
  • $\begingroup$ The Map displays the Route regardless of LNAV. It shows a small distance behind the airplane, if there's a WPT within that distance, it will be displayed. If you crank up the range it'll help. Enroute FMC WPT passage takes place upto 21nm abeam the waypoints. What that means is that the next WPT becomes Active (magenta) while the passed WPT symbol becomes white and the now active WPT moves to line 1L i.e. the 'to' WPT on the CDU. Map Center mode displays the map superimposed on a 360deg compass rose and half the selected range is ahead of the airplane and half behind. $\endgroup$
    – skipper44
    Sep 4, 2021 at 19:09
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    $\begingroup$ @skipper44: Many thanks for the clarification. I've updated the answer. Also thanks for posting an answer. $\endgroup$
    – user14897
    Sep 4, 2021 at 21:07
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The B787 is one type of implementation, others could vary. Yes, if you were able to zoom out enough you would see previous WPTs though they are no longer displayed on the active plan 'legs page' of the FMC CDU. Though I've shown the normal ND Map mode display below, there is another mode called Centered Map mode that displays the airplane at the center of a '360deg compass rose' type display with half the selected range in front and half the selected range behind the airplane and the active route displayed for both forward and aft areas.

  • Map mode with 'from' WPT visible.

ND Map display mode.

The FMC/CDU does not keep a history of the flown route, but at any given time, two routes, named RTE 1 and RTE 2 can be stored on the FMC for rapid activation, and one of these, conventionally RTE 1 is activated to become the 'live route'.

So though on the active flown route there's no realtime history, of WPTs passed, instead, the route as originally planned can be viewed on the CDU and ND Plan mode (North UP) by looking at RTE 1.

Your question "If they're not visible now, why so?", could instead be applied to the CDU, in which case the argument against would be:
(a) Having this RTE 1 available for rapid activation in case of a loss of the FMC Route, is the most likely scenario for it's use.
(b) For the en-route diversion scenarios The B787 has other dedicated methods.
(c) This system implementation is more suitable for long range flights having many possible diversion scenarios. A turnback and diversion back following the route history is unlikely in today's airspace structure and air traffic.

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