# Flight Log aLTITUDES

**URL:** <https://discussions.flightaware.com/t/flight-log-altitudes/4641>\
**Category:** General\
**Created:** [January 28, 2008, 7:27pm UTC](https://discussions.flightaware.com/t/flight-log-altitudes/4641 "2008-01-28T19:27:17Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![TomG628](https://avatars.discourse-cdn.com/v4/letter/t/b77776/32.png) [@TomG628](https://discussions.flightaware.com/u/TomG628)\
**Post date:** [January 28, 2008, 7:27pm UTC](https://discussions.flightaware.com/t/flight-log-altitudes/4641/1 "2008-01-28T19:27:17Z")

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Sometimes the altitudes in the flight log alt column show a strange variation. For example on descent, it may show 40,000, 36,000, 25,000, 12,000 showing a progressing descent, then an instant jump up to 30,000, followed by the rest of the descent profile. 8,000 for example, and maybe another spike to a higher alt before the descent resumes normally again. What causes this? Thanks. Tom

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**Author:** ![wazzu90](https://avatars.discourse-cdn.com/v4/letter/w/bc79bd/32.png) [@wazzu90](https://discussions.flightaware.com/u/wazzu90)\
**Post date:** [January 28, 2008, 9:08pm UTC](https://discussions.flightaware.com/t/flight-log-altitudes/4641/2 "2008-01-28T21:08:40Z")

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Essentially, ATC clears them to that ‘jump’ altitude at that point.

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**Author:** ![damiross](https://avatars.discourse-cdn.com/v4/letter/d/b9bd4f/32.png) [@damiross](https://discussions.flightaware.com/u/damiross)\
**Post date:** [January 28, 2008, 9:24pm UTC](https://discussions.flightaware.com/t/flight-log-altitudes/4641/3 "2008-01-28T21:24:56Z")

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As state elsewhere in this forum, what happens is that ATC radar loses the altitude of the aircraft. It substitutes the filed altitude.

Use the “search” button above to locate further data.

[Here is one such discussion](http://discussions.flightaware.com/viewtopic.php?t=4322&highlight=altitude)

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**Author:** ![magnetoz](https://avatars.discourse-cdn.com/v4/letter/m/13edae/32.png) [@magnetoz](https://discussions.flightaware.com/u/magnetoz)\
**Post date:** [January 28, 2008, 9:25pm UTC](https://discussions.flightaware.com/t/flight-log-altitudes/4641/4 "2008-01-28T21:25:48Z")

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I always figured that the altitudes were actually mode C reported altitudes, not ATC cleared altitudes, and that strange deviations were a result of reporting errors…

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**Author:** ![TomG628](https://avatars.discourse-cdn.com/v4/letter/t/b77776/32.png) [@TomG628](https://discussions.flightaware.com/u/TomG628)\
**Post date:** [January 28, 2008, 11:47pm UTC](https://discussions.flightaware.com/t/flight-log-altitudes/4641/5 "2008-01-28T23:47:26Z")

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Thanks for the help. Regards, tom