M
Magnetic variation - The horizontal angle between the true north and magnetic north measured east or west according to whether magnetic north lies east or west of true north.
Maltese cross - The Maltese cross is used to identify the final approach fix in a non-precision instrument approach (one that lacks precision vertical guidance), in contrast to the use of a lightning bolt type icon, which identifies the final approach fix in a precision approach.
Mandatory altitude - An altitude depicted on an instrument Approach Procedure Chart requiring the aircraft to maintain altitude at the depicted value.
Manoeuvring area - That part of an aerodrome to be used for the take-off, landing and taxiing of aircraft, excluding aprons
MAXIMUM AUTHORIZED ALTITUDE- MAA - A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment.
Meteorological report -
Middle marker - MM - A marker beacon that defines a point along the glideslope of an ILS normally located at or near the point of decision height (ILS Category I). It is keyed to transmit alternate dots and dashes, with the alternate dots and dashes keyed at the rate of 95 dot/dash combinations per minute on a 1300 Hz tone, which is received aurally and visually by compatible airborne equipment.
Minimum crossing altitude - MCA - The lowest altitude at certain fixes at which an aircraft must cross when proceeding in the direction of a higher minimum en route IFR altitude.
Minimum descent altitude/height - MDA/H - The lowest altitude, expressed in feet above mean sea level, to which descent is authorized on final approach or during circle-to-land maneuvering in execution of a standard instrument approach procedure where no electronic glideslope is provided.
minimum en-route altitude - MEA - the altitude for an en-route segment that provides adequate reception of relevant navigation facilities and ATS communications, complies with the airspace structure and provides the required obstacle clearance.
Minimum Obstacle Clearance Altitude - MOCA - The lowest published altitude in effect between fixes on VOR airways or route segments that
meets obstacle (like a building or a tower) clearance requirements for the entire route segment.
Minimum reception altitude - MRA - is the lowest altitude on an airway segment where an aircraft can be assured of receiving signals
from navigation aids like VOR or NDB.
Minimum safe altitude - MSA - Altitudes depicted on approach charts which provide at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the navigation facility upon which a procedure is predicated.
Minimum off-route altitude - MORA -
The MORA provides reference point clearance within 10 NM of the route centerline (regardless of the route width) and end fix.
The GRID MORA provides reference point clearance within the section outlined by latitude and longitude lines.
Minimum sector altitude - The lowest altitude which may be used under emergency conditions which will provide a minimum clearance
of 300 m (1,000 feet) above all obstacles located in an area contained within a sector of a circle of 46 km (25 NM) radius centered on a radio aid to navigation.
Missed approach -
a. A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing. The route of flight and altitude are shown on instrument approach procedure charts. A pilot executing a missed approach prior to the Missed Approach Point (MAP) must continue along the final approach to the MAP.
b. A term used by the pilot to inform ATC that he/she is executing the missed approach.
c. At locations where ATC radar service is provided, the pilot should conform to radar vectors when provided by ATC in lieu of the published missed approach procedure.
Missed approach point - MAP - A point prescribed in each instrument approach procedure at which a missed approach procedure shall be executed if the required visual reference does not exist.
Mode (SSR mode) - The letter or number assigned to a specific pulse spacing of the interrogation signals transmitted by an interrogator.
There are 4 modes, A, B, C and D specified in Annex 10, corresponding to four different interrogation pulse spacings.