Microwave landing system (MLS).  A precision instrument  approach system operating in the microwave spectrum which  normally consists of an azimuth station, elevation station,  and precision distance measuring equipment. Mileage breakdown. A fix indicating a course change  that appears on the chart as an “x” at a break between two  segments of a federal airway. Military operations area (MOA).  Airspace established for  the purpose of separating certain military training activities  from IFR traffic. Military training route (MTR).  Airspace of defined vertical  and lateral dimensions established for the conduct of military  training at airspeeds in excess of 250 knots indicated airspeed  (KIAS). Minimum altitude.  An altitude depicted on an instrument  approach chart with the altitude value underscored. Aircraft are  required to maintain altitude at or above the depicted value. Minimum crossing altitude (MCA).  The lowest allowed  altitude at certain fixes an aircraft must cross when proceeding  in the direction of a higher minimum en route altitude  (MEA). Minimum descent altitude (MDA).  The lowest altitude (in  feet MSL) to which descent is authorized on final approach,  or during circle-to-land maneuvering in execution of a  nonprecision approach. Minimum en route altitude (MEA).  The lowest published  altitude between radio fixes that ensures acceptable  navigational signal coverage and meets obstacle clearance  requirements between those fixes. Minimum obstruction clearance altitude (MOCA).  The  lowest published altitude in effect between radio fixes on VOR  airways, off-airway routes, or route segments, which meets  obstacle clearance requirements for the entire route segment  and which ensures acceptable navigational signal coverage  only within 25 statute (22 nautical) miles of a VOR. Minimum reception altitude (MRA).  The lowest altitude  at which an airway intersection can be determined. Minimum safe altitude (MSA). The minimum altitude  depicted on approach charts which provides at least 1,000 feet  of obstacle clearance for emergency use within a specified  distance from the listed navigation facility. Minimum vectoring altitude (MVA).  An IFR altitude lower  than the minimum en route altitude (MEA) that provides  terrain and obstacle clearance. Minimums section.  The area on an IAP chart that displays the  lowest altitude and visibility requirements for the approach. Missed approach.  A maneuver conducted by a pilot when an  instrument approach cannot be completed to a landing. Missed approach point (MAP).  A point prescribed in each  instrument approach at which a missed approach procedure  shall be executed if the required visual reference has not  been established. Mixed ice.  A mixture of clear ice and rime ice. MLS.  See microwave landing system. MM.  Middle marker. MOA.  See military operations area. MOCA.  See minimum obstruction clearance altitude. Mode C.  Altitude reporting transponder mode. MRA.  See minimum reception altitude. MSA.  See minimum safe altitude. MSL.  See mean sea level. MTR.  See military training route. Multi-function display (MFD).  Small screen (CRT or LCD)  in an aircraft that can be used to display information to the  pilot in numerous configurable ways. Often an MFD will be  used in concert with a Primary Flight Display. MVA.  See minimum vectoring altitude. NACG.  See National Aeronautical Charting Group. NAS.  See National Airspace System. National Airspace System (NAS).  The common network of  United States airspace—air navigation facilities, equipment  and services, airports or landing areas; aeronautical charts,  information and services; rules, regulations and procedures,  technical information; and manpower and material.  G-12