[Code of Federal Regulations] [Title 14, Volume 2] [Revised as of January 1, 2007] From the U.S. Government Printing Office via GPO Access [CITE: 14CFR73.3] [Page 480-481] TITLE 14--AERONAUTICS AND SPACE CHAPTER I--FEDERAL AVIATION ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PART 73_SPECIAL USE AIRSPACE--Table of Contents Subpart A_General Sec. 73.3 Special use airspace. (a) Special use airspace consists of airspace of defined dimensions identified by an area on the surface of the earth wherein activities must be confined because of their nature, or wherein limitations are imposed upon aircraft operations that are not a part of those activities, or both. (b) The vertical limits of special use airspace are measured by designated altitude floors and ceilings expressed as flight levels or as feet above mean sea level. Unless otherwise specified, the word ``to'' (an altitude or flight level) means ``to and including'' (that altitude or flight level). (c) The horizontal limits of special use airspace are measured by boundaries described by geographic coordinates or other appropriate references that clearly define their perimeter. [[Page 481]] (d) The period of time during which a designation of special use airspace is in effect is stated in the designation.