Codes in the range QAA–QNZ are reserved for aeronautical use; QOA–QQZ for maritime use and QRA–QUZ for all services.
"Q" has no official meaning, but it is sometimes assigned a word with [[mnemonic]] value, such as "Queenquestion" or "query", for example in QFE: Queen's"query field elevation, or "Query", "Question", "reQuest".<ref>{{cite web |url=http://www.boeing.com/commercial/aeromagazine/aero_16/polar_story.html |title=Aero 16 – Polar Route Operations|first=277808-Elizabeth A. |last=Franklin |access-date=5 September 2016 |url-status=dead |archive-url=https://web.archive.org/web/20011113093037/https://www.boeing.com/commercial/aeromagazine/aero_16/polar_story.html |archive-date=13 November 2001}}</ref>
