A unit of measure of air speed. Mach 1 is the speed of sound - Mach .92 is the Citation X, the world's fastest business jet.

The ratio of one's true airspeed to the speed of sound.

Periodic checks that have to be done on all aircraft after a certain amount of time or usage. Airlines and airworthiness authorities casually refer to the detailed inspections as "checks", commonly one of the following: A check, B check, C check, or D check. A and B checks are lighter checks, while C and D are considered heavier checks.

An international radiotelephone signal word used by aircraft and ships in distress. Repeat MAYDAY to indicate an imminent and grave danger that requires assistance.

Middle East Business Aviation Association

Term used when an aircraft has to be grounded for unscheduled maintenance issues. This can be a nuisance to operators, brokers, and their clients because they will have to find replacement lift for the scheduled itinerary.

Medical evacuation. Usually for emergencies, it is the ambulance flight service of many helicopter and jet charter companies.

Minimum Equipment List. Identifies equipment installed on the aircraft that may under certain conditions be inoperative and still allow the aircraft to be airworthy. Removal of any item of equipment that affects the airworthiness of an aircraft requires following an approved procedure. A properly certified maintenance person must record the removal in accordance with proper CFR (Code of Federal regulations). A person authorized by FAR’s must make the appropriate adjustments to the aircraft’s weight and balance information and the aircraft for return to service. The operator must evaluate any proposed deactivation to assure there is no adverse effect that could render another system less than fully capable of its intended function. As long as an item is on the list, if it is broken the plane will be allowed to fly and the item can be repaired in a designated time frame. An MEL could also be thought of as an "inoperative equipment list" since the plane can fly and be air worthy without the listed items beings in working order.

This process bonds pieces of metal together instead of riveting, thereby making the assembly stronger and more durable in some aircraft.

Format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting. Reports typically come from airports or permanent weather observation stations. Reports are typically generated once an hour; if conditions change significantly, however, they can be updated in special reports called SPECI's.

A sudden, violent downdraft of air over a small area. Microbursts are difficult to detect and predict with standard weather instruments and are especially hazardous to airplanes during landing or takeoff. Winds have been known to reach up to 150 knots.

An aircraft with a certified takeoff weight ranging between 41,000 lbs. to 255,000 lbs. They typically have seating capacity for 7 to 9 passengers. See examples of Midsize Jets on JetRequest.com.

MEL. Identifies equipment installed on the aircraft that may under certain conditions be inoperative and still allow the aircraft to be airworthy. Removal of any item of equipment that affects the airworthiness of an aircraft requires following an approved procedure. A properly certified maintenance person must record the removal in accordance with proper CFR (Code of Federal regulations). A person authorized by FAR’s must make the appropriate adjustments to the aircraft’s weight and balance information and the aircraft for return to service. The operator must evaluate any proposed deactivation to assure there is no adverse effect that could render another system less than fully capable of its intended function. As long as an item is on the list, if it is broken the plane will be allowed to fly and the item can be repaired in a designated time frame. An MEL could also be thought of as an "inoperative equipment list" since the plane can fly and be air worthy without the listed items beings in working order.

The minimum vertical or horizontal distance allowed between two aircraft.

A measurement of weight at a specific distance (moment arm) from a reference point. This measurement is used to verify the aircraft is within the Center of Gravity (CG) limits. Reference points vary between aircraft.

An object (as in a wing or fuselage) whose skin supports the load as opposed to an internal frame.

An aeroplane with one wing (or pairs of wings).

Maintenance, Repair, and Overhaul. Some companies specialize in the fixing of any sort of mechanical or electrical device should they become out of order or broken (known as repair, unscheduled or casualty maintenance). They also take care of performing routine actions which keep the device in working order (known as scheduled maintenance) or prevent trouble from arising (preventive maintenance). These companies are called MROs.

Manufacturer Serial Number

Maintenance Service Plan offered by Honeywell for their engines.

Maximum Takeoff Weight or Maximum Takeoff Mass. The maximum weight at which the pilot of the aircraft is allowed to attempt to take off, due to structural or other limits.

A trip that has an itinerary requiring more than the two stops of a traditional round trip. Find transient aircraft available for your Multi-Leg trip on the Transient Availability page of JetRequest.com.