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 drag.  The point on the total drag curve where  the lift-to-drag ratio is the greatest. At this speed, total drag  is minimized.  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 equipment list (MEL).  A list developed for larger  aircraft that outlines equipment that can be inoperative for  various types of flight including IFR and icing conditions. This  list is based on the master minimum equipment list (MMEL)  developed by the FAA and must be approved by the FAA for  use. It is specific to an individual aircraft make and model.  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.  Moment.  The product of the weight of an item multiplied  by its arm. Moments are expressed in pound-inches (lb-in).  Total moment is the weight of the airplane multiplied by the  distance between the datum and the CG.  Moment arm.  The distance from a datum to the applied force.  Moment index (or index).  A moment divided by a constant  such as 100, 1,000, or 10,000. The purpose of using a moment  index is to simplify weight and balance computations of  airplanes where heavy items and long arms result in large,  unmanageable numbers.  Monocoque.  A shell-like fuselage design in which the  stressed outer skin is used to support the majority of imposed  stresses. Monocoque fuselage design may include bulkheads  but not stringers.  Monoplanes.  Airplanes with a single set of wings.  Movable slat.  A movable auxiliary airfoil on the leading edge  of a wing. It is closed in normal flight but extends at high  angles of attack. This allows air to continue flowing over the  top of the wing and delays airflow separation.  MRA.  See minimum reception altitude.  MSA.  See minimum safe altitude.  MSL.  See mean sea level.  G-20 