Editing Airspace class (section)

===United States===
[[File:Airspace classes (United States).png|thumb|500px|Airspace classes in the United States]]

{{Main|Airspace class (United States)}}

The [[United States|U.S.]] adopted a slightly modified version of the ICAO system on September 16, 1993, when regions of airspace designated according to older classifications were converted entirely. The exceptions are some [[terminal radar service area]]s (TRSA), which have special rules and still exist in a few places.

*With some exceptions, '''Class A''' airspace is applied to all airspace between {{convert|18000|ft|m|-2}} and {{Flight Level|600|prefix=fulllk}}. Above {{Flight level|600}}, the airspace reverts to Class E.<ref name=classE_FL600>FAA Order 7400.11, Subpart E, Para. 6001</ref> The [[transition altitude]] is also consistently {{convert|18000|ft|m|-2}} everywhere. All operations in US Class A airspace must be conducted under IFR. SVFR flight in Class A airspace is prohibited.
*'''Class B''' airspace is used to control the flow of traffic around major [[airport]]s. The airspace is charted on a [[visual flight rules|VFR]] sectional chart with a series of blue lines. Within these blue lines, the floor and the ceiling of the Class B airspace is defined. The lateral boundaries of Class B airspace are individually tailored to facilitate arriving and departing traffic operating under [[instrument flight rules|IFR]]. Class B airspace extends from the surface to generally {{convert|10000|ft|m|-2}} [[sea level|MSL]]. In [[Denver, Colorado]] and [[Salt Lake City, Utah]], the ceiling is at {{convert|12000|ft|m|-3}} MSL, while in [[Phoenix, Arizona]], the ceiling is at {{convert|9000|ft|m|-3}} MSL.<ref>{{cite web|url=http://pilot2pilotblog.blogspot.com/2013/06/class-b-airspace.html |title=Pilot2Pilot – For Pilots by Pilot: Class B Airspace |publisher=Pilot2pilotblog.blogspot.com |access-date=2014-03-04}}</ref> Charts must be consulted for the most current floor and ceiling information. Aircraft must establish two-way radio communication with ATC and obtain a clearance to enter Class B airspace. All aircraft operating inside or within 30 NM of the primary Class B airport(s) are required to have a transponder with Mode C. The 30 NM Mode C Veil is denoted on VFR charts by a thin magenta line. VFR traffic must remain clear of clouds and maintain 3 SM of visibility while operating within Class B airspace.
*'''Class C''' airspace is used around airports with a moderate traffic level.
*'''Class D''' is used for smaller airports that have a control tower. The U.S. uses a modified version of the ICAO class C and D airspace, where only radio contact with ATC rather than an ATC clearance is required for VFR operations.
*Other controlled airspace is designated as '''Class E''', this includes a large part of the lower airspace. Class E airspace exists in many forms. It can serve as a surface-based extension to Class D airspace to accommodate IFR approach/departure procedure areas. Class E airspace can be designated to have a floor of {{convert|700|ft|m|-1|abbr=on}} [[above ground level|AGL]] or {{convert|1200|ft|m|-1|abbr=on}} AGL, or a customized floor of any other altitude. Class E airspace exists above Class G surface areas from {{convert|14500|ft|m|-2|abbr=on}} [[sea level|MSL]] to {{convert|18000|ft|m|-2|abbr=on}} MSL. Federal [[airway (aviation)|airways]] from {{convert|1200|ft|m|-1|abbr=on}} AGL to {{convert|18000|ft|m|-2|abbr=on}}  MSL within {{convert|4|mi|km|0}} of the centerline of the airway is designated Class E airspace. Airspace at any altitude over {{Flight level|600}} (the ceiling of Class A airspace) is designated Class E airspace.<ref name=classE_FL600/>
*The U.S. does not use ICAO '''Class F'''.
*'''Class G''' (uncontrolled) airspace is mostly used for a small layer of airspace near the ground, but there are larger areas of Class G airspace in remote regions.