Mach Number; the speed of a vehicle expressed in relation to the speed of sound under the same ambient conditions. Under standard sea level conditions (15°C) Mach 1 is approximately 340.5m/s (1,117ft/s) or 661.4kts (1,225.5km/h). In the standard atmosphere the velocity corresponding to Mach 1 decreases to the tropopause at 36,090ft (11,000m), above which the temperature remains constant at -56.3°C and the speed of sound is 295.5m/s (969ft/s) or 573.75kts (1,063.2km/h)

(1) Military Airlift Command (now incorporated in AMC; USAF) or (2) mean aerodynamic chord

McDonnell Aircraft Company

magnetic anomaly detector, also mutually assured destruction

microwave aircraft digital guidance equipment

Modular Airborne FireFighting System

Marine Air Group (USMC)

man-portable air defence system

(1) Military Aid Program (US) or (2) Military Assistance Program (US) or (3) Mutual Assistance Program

Moscow Aircraft Production Organisation

Mid-Air Recovery/Retrieval System (USN/USAF)

manoeuvring re-entry vehicle (US)

Military Air Transport Service (USAF, preceded MAC)

Multi-Axis Thrust Vectoring (USAF)

Military Air Traffic Zone

(1) Marine Air Wing (USMC) or (2) mission-adaptive wing (a Boeing/USAF/NASA variable-camber experiment) or (3) Military Airlift Wing (USAF)

missile approach warning system

 internationally recognised distress call for urgent assistance (Anglicised from the French m'aidez!, literally: to my aid)

 millibar

Messerschmitt-Bölkow-Blohm (part of DASA)

Marine Corps Air Station (USMC)

mine countermeasures

(1) McDonnell Douglas Corporation or (2) miniature detonating chord (BAe, used to shatter canopy prior to ejection)

McDonnell Douglas Helicopter Co

Military Emergency Diversion Airfield

 MEDical EVACuation

mission equipment package (US)

multiple ejector rack

Maritime Electronic Warfare Support Group (UK)

(1) maritime exclusion zone (2) missile engagement zone

(1) medium frequency or (2) multi-function

multi-function display

machine-gun

modular guided glide bomb

megahertz

MILitary Strategic and TACtical Relay (US)

military standard

multiple independently-targeted re-entry vehicles

Missile Squadron (US)

one which is aborted, for whatever reason, followed by an overshoot

one with an automatically varying section profile to adapt to the requirements of each flight condition

multiple-launch rocket system

microwave landing system

mid-life update

maximum landing weight

maintenance man-hours per flight hour

Multi-mission Maritime Aircraft (USN programme for replacement of P-3 Orion)

maximum operating Mach number

mast-mounted sight (on helicopter)

Multi-Mission Surveillance Aircraft (special mission Metro 23)

millimetre-wave (radar)

Mach number never to be exceeded; not reached in normal flying, but available in emergency

maximum permitted operating Mach number

Memorandum of Agreement

Ministry of Defence

modification

Ministry of Defence (Procurement Executive)

 method of construction in which all structural strength is in the outer skin and immediately underlying frames and stringers, without interior structure or bracing

Memorandum of Understanding

(1) maritime patrol aircraft or (2) man-powered aircraft

Missile Practice Camp

multi-purpose display

maximum power reserve

maritime reconnaissance

Medium-Range Air-to-Air Missile

Medium-Range Air-to-Surface Missile (BGM-109H/L)

Multi-Role Fighter (USAF projected F-16 replacement)

multiple rocket launcher

maximum ramp weight

minimum safe altitude

multinational staged improvement programme or multistage improvement programme (US/Europe)

mean sea level

manufacturer's serial number (largely used in US, usually referred to as construction number in UK)

Modular Stand-Off Weapon (US)

modular self-protection system

Military Training Area

Millimetric, Modular or Multi-sensor Target Acquisition System

mean time between overhauls

mean time between removals

moving target detection

moving target indicator (a radar facility)

maximum take-off gross weight

maximum take-off weight

multiple target tracking

Motoren- und Turbinen-Union (Germany)

Maintenance Unit (RAF)

(1) Missile Wing (USAF) or (2) Mehrzweckwaffe (German multi-purpose weapon)

maximum zero fuel weight

Navy, Army & Air Force Institutes

(1) Naval Air Command (UK) or (2) North Atlantic Council (NATO)

National Advisory Committee for Aeronautics (now NASA)

Naval Air Development Center (USN)

naval aircrew common ejection seat (USN)

Naval Air Depot (USN)

Nato Air Defence Ground Environment

NATO Airborne Early Warning Force

Naval Air Facility (US)

Nanchang Aircraft Manufacturing Co (China)

NATO MRCA development & Procurement Management Agency (now superseded by NATO Eurofighter and Tornado Management Agency)

Naval Air Station (USN)

National Aeronautics and Space Administration

Naval Air Systems Command (USN)

National Aero-Space Plane, now cancelled (US)

(1) Naval Air Training Command or (2) Naval Air Test Center (both USN)

North Atlantic Treaty Organisation

NAVigation AID

NAVigation EXercise

NAVigation Satellite Timing And Ranging (US-DoD, now known as GPS)

navigation & weapon aiming sub-system

Naval Air Warfare Center (USN)

National Business Aircraft Association (US)

nuclear, biological and chemical (warfare)

Non-Commissioned Officer

non-co-operative target identification/recognition (radar facility)

Non-Developmental Airlift Aircraft (USAF requirement)

non-directional beacon

non-destructive testing

National Emergency Airborne Command Post (US)

NATO EFA/Eurofighter Management Agency(now superseded by NATO Eurofighter and Tornado Management Agency)

NATO Eurofighter and Tornado Management Agency

NATO Frigate Helicopter

Naval Flight Officer (USN)

Naval Fighter Weapons School (USN 'Topgun' academy)

no-fly zone

night imaging through electro-optics

non-line-of-sight

nautical mile, equal to 1,853m (6,080ft)

National Oceanic and Atmospheric Administration (US)

nap-of-the-earth (helicopter or aircraft tactic using natural cover of hills, trees etc)

 -- see footprint (noise)

no live operator

North American Aerospace Defense Command (US-DoD)

NOtice To AirMen, an advisory notice giving information on the establishment, condition or change in any aeronautical facility, service, procedure or hazard (ICAO)

NO TAil Rotor (MDH)

Non-Proliferation Treaty

National Security Agency (US)

Naval Test Pilots School (at Patuxent River NAWC)

night vision goggles

night vision system

Naval Weapons Center (USN)

operations & maintenance

outside air temperature

onboard inert gas generating system

 one pivoted at mid-point so that one half is swept back and the other forwards, also referred to as slew wing

on-board oxygen generation system

Officer Commanding

Obstacle Clearance Altitude (Height)

 unit of visible sky area representing one eighth of total area visible to horizon

(1) Operational Conversion Unit (RAF) or (2) operational capability update (US)

one engine inoperative

Operational Evaluation Unit (UK)

agreement with customer nation to give local workshare, helping to offset purchase cost of an imported aircraft/system and create local employment

Operations Group (USAF)

out of ground effect (relates to helicopter hovering performance far above nearest land or water surface)

Oficinas Gerais de Material Aeronautico (Portugal)

Opytno-Konstruktorskoye Byuro - Russian designation for an experimental aircraft or missile design bureau

long-range hyperbolic radio navigation aid

Operational Requirement (RAF)

operational readiness platform (RAF)

Operational Support Squadron (USAF)

over-the-horizon -- backscatter (long-range radar)

over-the-horizon targeting

 ILS marker situated normally at about 8.3km (4^½nm) out from runway threshold and on centreline

operating weight empty