Today's BA219 from LHR to DEN (2018-03-20) appeared to fly 5 zigzags just before and over the Hudson Bay in Canada at around 18:15z. Prior to that, its flight path matched its planned route very closely.

I know that congestion avoidance can sometimes lead to flights being asked to fly doglegs (as in Why did this plane fly in a zigzag pattern?), but this flight was still 3 hours from its destination and still exceeding planned speed when it appeared to fly zigzags. I don't see any weather issues on radar at the time.

After the zigzags seen in the FlightAware capture, the flight track straightened up and flew parallel to its planned route. This appears to be a track data problem, not the actual plane's path.

BA219 flight path over Hudson Bay

But on FR24 that path is not there:

enter image description here

I've seen 'Why do aircraft on Flight Radar 24 jump around randomly sometimes?', since they are different services, what could be the reasons for FlightAware to behave like this? Also note the linked FR24 post is a different more jagged path than the one here.

FlightAware tracks from other flights show similar zigzags in the Hudson Bay area. Presumably this is just noisy tracking data. Any idea why that happens in this particular location?

  • $\begingroup$ Thanks, @Sanchises. I started with that question. The answer in that one is that the zigzag was a dogleg for congestion avoidance. I mention in my question that that seems less likely here since this flight was 3 hours from landing and maintaining an above-planned speed. $\endgroup$ Mar 20, 2018 at 18:51
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    $\begingroup$ Possible duplicate of Why do aircraft on Flight Radar 24 jump around randomly sometimes? $\endgroup$
    – user14897
    Mar 20, 2018 at 18:54
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    $\begingroup$ FlightAware tracks for other flights show similar zigzags in the Hudson Bay area. Presumably @ymb1 is right that it's a data issue and not the real flight path. I'm still curious why the data would get sketchy in that area. $\endgroup$ Mar 20, 2018 at 19:52
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    $\begingroup$ It does seem to be smoothing things. The track log shows single entries for a course 150 degrees, from Edmonton Center. Later entries from Edmonton are better but still a bit wacky. $\endgroup$
    – fooot
    Mar 20, 2018 at 21:57
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    $\begingroup$ @NedGladstone - see this: flightaware.com/about/faq#anomaly $\endgroup$
    – user14897
    Mar 22, 2018 at 0:26

1 Answer 1


It looks as if the GPS location was only updated at intervals, and the software extrapolated the missing path information using bezier curves.

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    $\begingroup$ Even in that case, why would it assume it wasn't flying the original path? A Bezier can be a straight line if the control points are in a line, and in this case, they should be in a line. $\endgroup$ Jul 14, 2018 at 19:58

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