FAA Chart Users’ Guide - VFR Symbology - Flyway Planning Charts 44 AIRSPACE INFORMATION ALTITUDE IN HUNDREDS OF FEET MSL. (A minus sign in front of the  figure used to indicate “from  surface to but not including...”) Floors extending “upward and above” a certain altitude are pre- ceded by a +. Operations at or below these altitudes are outside  of the Class B Airspace.) All radials are magnetic. All mileages are nautical  (NM). (Mode C see  FAR 91.215/AIM) Appropriate notes as required may be shown. (Mode C see  FAR 91.215/AIM) Appropriate notes as  required may be shown. Example: Washington DC Appropriate notes as required may be shown. Note: Delimiting line not shown when it coincides with Internation- al Boundary, projection lines or other linear features. Special Airspace Areas Special Flight Rules Area (SFRA) Relating to National Security Class D Airspace Class E Surface (SFC) Airspace  Class C Airspace Class B Airspace