Mode C veil

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Mode C veil refers to a kind of airspace which surrounds most primary Class B airports within United States. This airspace extends horizontally to a circle of 30 NM radius centered on the airport, and extends vertically from the surface up to 10,000 feet MSL.[1] The name refers to the mode of transponder operation which is required within this airspace (i.e., with very limited exceptions, all aircraft operating within this airspace must have an altitude reporting Mode C transponder in operation). Out of 37 existing (as of late 2014) Class B airports in the United States,[2] 35 airports (i.e., all but 2) have Mode C veil centered on them.[3] The only two airports that do not are Houston Hobby Airport[4] and Miramar Naval Air Station.[5][6]


  1. ^ 14 C.F.R. 91.215(b)(2)
  2. ^ FAA's order JO 7400.9Y, effective 2014-09-15, accessed 2014-10-29
  3. ^ CFR Title 14 Appendix D to Part 91, Section 1
  4. ^ Which has it de facto, although not necessarily de jure – but will soon have it de jure as well according to 78 F.R. 14910 ("the FAA plans to add the William P. Hobby Airport to the list of airports identified in Title 14 of the Code of Federal Regulations, Part 91, Appendix D, Section 1").
  5. ^ As of November 2013, both of these exceptions have Mode C veils centered on them on the sectional, WAC, and Low IFR charts, which is inconsistent with CFR and as such is either cartographic mistake, or regulatory mistake, or both.
  6. ^ In a separate action (79 F.R. 57431) FAA updated CFR Title 14 Appendix D to Part 91, Section 1 to include Houston–Hobby and Miramar on the list, effective 2014-11-13.