U.S.
Department of Transportation

Term or Terms  Definition 
Broadcast (ADS-B)  and vertical position, horizontal and vertical velocity) and other information. ADS-B is Automatic in that it requires no external stimulus to elicit a transmission. ADS-B is Dependent because it relies on on-board navigation sources.  ADS-B Surveillance information is provided, via data link, to any users (either aircraft or ground-based) within range of the Broadcast signal. 
Available Landing Distance (ALD)  ALD is that portion of a runway available for landing and roll-out for aircraft cleared for land and hold short operations (LAHSO). This distance is measured from the landing threshold to the hold-short point. 
Category I Instrument Approach  A Category I instrument approach is any authorized precision or nonprecision instrument approach which is conducted with a minimum height for IFR flight not less than 200 feet (60 meters) above the touchdown zone and a minimum visibility/ RVV not less than 1/2 statute mile or RVR 1800 (for helicopters, 1/4 statute mile or RVR 1600). 
Certificate Holder  In these operations specifications the term "certificate holder" shall mean the holder of the certificate described in Part A paragraph A001 and any of its officers, employees, or agents used in the conduct of operations under these operations specifications. 
Class I Navigation  Class I navigation is any en route flight operation or portion of an operation that is conducted entirely within the designated Operational Service Volumes (or ICAO equivalents) of ICAO standard airway navigation facilities (VOR, VOR/DME, NDB). Class I navigation also includes en route flight operations over routes designated with an "MEA GAP" (or ICAO equivalent).  En route flight operations conducted within these areas are defined as "Class I navigation" operations irrespective of the navigation means used.  Class I navigation includes operations within these areas using pilotage or any other means of navigation which does not rely on the use of VOR, VOR/DME, or NDB.