I am examining some of the FAA's SID charts and, as far as I can deduce, each SID provides information concerning the altitude when it is necessary and, if not changed by the controller, each transition/route description will end with something such as "Maintain X altitude etc." which seems that it is the same as the Top Altitude.

Since this information is written in SID's textual description as "Maintain X altitude", why is there a need to exist also separately as Top Altitude?

  • 2
    $\begingroup$ I'm not sure what you're asking? The description page is just clarifying and reiterating the info on the graphic depiction. Are you just asking why they put it on there twice? $\endgroup$
    – TomMcW
    Commented Jul 26, 2018 at 19:05
  • $\begingroup$ Yes, but I guess what you said ("The description page is just clarifying and reiterating the info on the graphic depiction") answers that. So both the Top Altitude and the "Maintain X attitude" textual description refer to the same thing? $\endgroup$ Commented Jul 27, 2018 at 13:02
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    $\begingroup$ That's what I believe. $\endgroup$
    – TomMcW
    Commented Jul 27, 2018 at 19:00
  • $\begingroup$ @TomMcW thank you for your clarification, please feel free to post your comments as an answer, so I can mark it as the accepted one. $\endgroup$ Commented Aug 11, 2018 at 16:22

1 Answer 1


It is needed for the new climb-via instruction (c. 2014).

Instead of issuing different maintain altitudes to the aircraft based on the SID, direction, etc., a top altitude is charted. From the FAA AIM:

SIDs will have a "top altitude;" the "top altitude" is the charted "maintain" altitude contained in the procedure description or assigned by ATC.



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