Looking at the flight BY6272 BRS-PMI, it was considerably delayed and flew (according to the flight radar app) at 29,000 feet rather than its usual 40,000 for this same route. It is a Boeing 787 Dreamliner. Flight time is usually around an average of 2hours.

This flight is weekly. Why would it fly low on some weeks and high on others?

July 12, 2022: enter image description here

June 28, 2022: enter image description here

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    $\begingroup$ It sounds as though the airplane was not RVSM capable for some unknown system failure. $\endgroup$
    – wbeard52
    Jul 12, 2022 at 12:01
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    $\begingroup$ RVSM starts at 290. If you're non RVSM, you're stuck below that. $\endgroup$
    – John K
    Jul 12, 2022 at 12:31
  • $\begingroup$ I’d be hard-pressed to think this is an RVSM issue considering A/C in question is a B-787. It would seem this is more up to the individual airlines flight planning dept. for routing weather, scheduling, etc. $\endgroup$ Jul 12, 2022 at 19:14
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    $\begingroup$ How have you determined that this flight's normal altitude for this route is FL400? $\endgroup$
    – user22445
    Jul 12, 2022 at 19:46
  • $\begingroup$ Just spitballing... is 290 a limit for any MEL's on the 787? Like pressurization, maybe? (Flying with 1 pack deferred on the 737 limits us to 250; dunno if the Dreamliner might have a slightly higher limit due to differences in their systems.) $\endgroup$
    – Ralph J
    Jul 12, 2022 at 20:09


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