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I'm just curious if it's ever possible to file for, and/or fly, an altitude that is above an airway restriction. Say if the airway has an altitude restriction of FL410 or less. Is it ever possible to fly above that (with a capable plane, of course)? Thanks!

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MAA ( Maximum Authorized Altitude) for an airway is the highest authorized altitude to be flown on that particular airway/published route. Usually this limitation is to ensure adequate navigation signals. It's published on the IFR enroute chart for the airway/published route to which it applies. You can't fly along this airway/published route (using your own navigation equipment as the primary source) at an altitude higher than published (i.e., the MAA if one exists). Point-to-point RNAV (random-not using a published route) does not have an MAA.

Look at the IFR Enroute chart legend for the definition of MAA (Maximum Authorized Altitude) .

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  • $\begingroup$ So it seems that an RNAV point-to-point routing can NEVER be coincidental with an airway? Is this really the case? The pilot must make absolutely sure that their point-to-point never overlaps an airway? $\endgroup$
    – John Ward
    Jul 25 at 21:19
  • $\begingroup$ Let me give a very specific example that I've run into: Missouri, J181 from HLV to BAYLI has an MAA of 23000, with a standard MEA. That means that airplanes can ONLY ever fly between HLV and BAYLI from FL180 to FL230? That's it? Ever? $\endgroup$
    – John Ward
    Jul 25 at 21:44
  • $\begingroup$ @JohnWard - if there is an RNAV route (e.g. Q-route) that overlaps a J route (based on VORs) the "joint" route will be defined as such and any altitude limits (e.g. MEA, MAA) will be published on the chart. My answer is referring to a non-published RNAV Point-to-point route. For example, when over ABQ the pilot requests direct to DFW at FL 390 and gets cleared so by ATC, then that random route will be flown using some type of RNAV equipment. In this case there will be no published MAA. $\endgroup$
    – 757toga
    Jul 25 at 22:12
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    $\begingroup$ @JohnWard - in your HLV-BAYLI J181 example signal integrity is not assured above FL230. Using your VOR equipment as your primary source (J181 being VOR signal based), is not permitted (above FL230). If you are cleared HLV direct BAYLI (not via J181) and you are using your RNAV equipment (e.g. GPS, FMS, etc.) as your primary source of navigation, then the J181 MAA restriction does not apply. $\endgroup$
    – 757toga
    Jul 25 at 22:30
  • $\begingroup$ THANK YOU! Finally! LOL. That was my entire question! It CAN be coincidental that a route (using point-to-point) follows an airway. Thank you so much. (If you know, and wish to answer, is there some sort of notation one makes when filing such a plan and wishes to use point-to-point, but follow a portion of an airway? Or must they they list every single point to emphasize that they aren't following the airway restrictions?) Anyway, thank you again! $\endgroup$
    – John Ward
    Jul 26 at 1:12
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Yes, if as you say your aircraft can do that. The rules change somewhat as to separation, as above FL 450 navigation can be done point to point instead of by navaids. FL 600 or above is usually reserved for military and special purpose use.

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    $\begingroup$ Can you cite a FAR or other source saying that airspace above FL600 is "reserved"? It's Class E airspace, and to my knowledge there's no limitation on filing for it or flying in it besides the physical limitations of your aircraft. $\endgroup$
    – randomhead
    Jun 24 at 17:18
  • $\begingroup$ FAR §71.71 cites above FL600 as Class E airspace. And I was just curious as to why some airways even have a top altitude restriction. Radar coverage limitations? $\endgroup$
    – John Ward
    Jun 25 at 12:48
  • $\begingroup$ @randomhead faa.gov/air_traffic/publications/atpubs/atc_html/… $\endgroup$ Jun 25 at 18:08
  • $\begingroup$ @JohnWard I can only surmise there is an interest in keeping separation between garden variety jet aircraft, some of the more advanced ones that can fly higher, and the rarified ones that can operate above FL 600. $\endgroup$ Jun 25 at 18:10
  • $\begingroup$ @Juan nothing there says or (as I read it) even implies that civilian operating above FL600 are prohibited. $\endgroup$
    – randomhead
    Jun 25 at 19:28

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