This glossary covers 73 of the most common terms a student pilot or ATPL candidate will encounter: licences and ratings, regulatory frameworks, weather and operations codes, aerodynamic principles, navigation concepts, and airspace vocabulary. All definitions are simplified for learning. For regulatory matters, official EASA and ICAO documents are the authoritative source, and you should confirm current details with your ATO and national aviation authority.
Plain-English explanations of the most important terms a student pilot encounters: licences, training, weather codes, performance, navigation and airspace.
From PPL to full ATPL, and from EASA Part-FCL to ICAO standards, the regulatory and licencing framework explained without jargon.
METAR, TAF, NOTAM, QNH, CAVOK, ISA and more: the weather and ops codes you will read every time you fly.
VOR, ILS, RNAV, great circle, rhumb line, FIR, TMA and the ATC vocabulary that keeps the sky ordered.
Many of the terms below are explained in more depth in dedicated guides. If a term sends you deeper, these are the best next reads.
Aeromedical Centre
An approved medical facility authorised to issue or renew EASA pilot medical certificates. Initial Class 1 assessments must be conducted at an AeMC.
Aeromedical Examiner
A doctor approved by a national aviation authority to conduct medical examinations and issue or renew pilot medical certificates. Established Class 1 holders often use an AME for renewal examinations.
The angle between the chord line of a wing and the direction of the oncoming airflow. As angle of attack increases, lift increases up to the critical angle, beyond which the wing stalls.
Approved Training Organisation
A flight training school approved by a national aviation authority under EASA standards to deliver professional pilot training. All licences and ratings on the commercial path must be completed at an ATO.
Airline Transport Pilot Licence
The highest level of pilot licence, required to act as pilot-in-command of an aircraft in scheduled commercial air transport. ATPL theoretical knowledge also refers to the 14-subject exam syllabus that all professional pilots must pass under EASA Part-FCL.
Civil Aviation Authority
A national regulator responsible for implementing aviation safety rules and issuing pilot licences. In Europe, CAAs apply EASA regulations; outside EASA states, equivalent national bodies may set their own rules.
Calibrated Airspeed
Indicated airspeed corrected for instrument and installation errors. CAS is a closer representation of true airspeed at low altitudes and low speeds, and is the basis for published aircraft performance data.
Ceiling and Visibility OK
A METAR and TAF code meaning visibility is 10 km or more, no cloud below 5,000 ft or the minimum sector altitude, no cumulonimbus or towering cumulus, and no significant weather. It replaces the individual visibility, weather and cloud groups in the report.
The height above the ground of the lowest layer of cloud covering more than half the sky. Ceiling is a key factor in determining whether visual or instrument flight rules apply at a given aerodrome.
The point through which the total weight of an aircraft acts. Centre of gravity must remain within the manufacturer's approved limits throughout a flight for the aircraft to be controllable and structurally safe.
An authorisation issued by air traffic control for a pilot to proceed under specified conditions. No aircraft may enter controlled airspace or execute a significant manoeuvre without an ATC clearance.
Commercial Pilot Licence
A licence that permits the holder to fly an aircraft for remuneration or hire. It requires a minimum amount of flight experience and a skill test, and sits above the PPL but below the full ATPL.
Control Zone
Controlled airspace extending from the surface to a specified upper limit around an aerodrome. Flight within a CTR requires an ATC clearance and adherence to the zone's operating procedures.
Distance Measuring Equipment
A radio navigation system that measures slant-range distance from an aircraft to a ground station. DME readouts are used to verify position along airways and to support precision and non-precision approaches.
The angular difference between an aircraft's heading and its actual track over the ground, caused by a crosswind component. Pilots apply a drift correction angle into the wind to fly the intended track.
European Union Aviation Safety Agency
The EU agency responsible for civil aviation safety regulation across EASA member states. EASA sets the licencing framework in Part-FCL, the medical framework in Part-MED, and the training organisation requirements that ATOs must meet.
European Central Question Bank
The central pool of questions from which EASA national authority ATPL theoretical knowledge examinations are drawn. Study tools prepare students for questions aligned with the ECQB style.
Flight Information Region
An airspace of defined dimensions within which flight information and alerting services are provided. Every part of the earth's airspace falls within a FIR.
A surface of constant atmospheric pressure referenced to the standard datum of 1013.25 hPa, expressed in hundreds of feet. Flight Level 100 is nominally 10,000 ft at standard pressure and is used for vertical separation above the transition altitude.
Not a separate licence, but the status of holding a CPL with a multi-engine instrument rating and full ATPL theoretical knowledge passes, pending the flight experience needed for the full ATPL. The holder can serve as a co-pilot in commercial operations, and the licence unfreezes once the required total flight experience is met.
Global Navigation Satellite System
The family of satellite-based positioning systems, including GPS and Galileo, used to determine precise aircraft position. GNSS underpins modern RNAV operations and has largely reduced dependence on ground-based beacons.
The shortest route between two points on a sphere, formed by a plane passing through the centre of the earth. Great circle routes are the most fuel-efficient paths for long distances but require a continuously changing compass heading.
The classroom or online phase of pilot training where theoretical knowledge is taught before and alongside flight training. Ground school covering the 14 ATPL subjects must be completed at or through an ATO for the theory credit to count.
The actual speed of an aircraft over the ground, combining true airspeed with the wind component along the track. Ground speed determines arrival time and is used for fuel planning.
The direction in which the aircraft's nose is pointing, measured in degrees from north. Heading differs from track when a crosswind component pushes the aircraft sideways.
Indicated Airspeed
The airspeed shown directly by the pitot-static airspeed indicator, before corrections. IAS is the primary reference speed pilots use in the cockpit for take-off, approach and limiting speeds.
International Civil Aviation Organization
The United Nations specialised agency that sets international standards and recommended practices for civil aviation, including licencing, airspace, communications and meteorological codes.
Instrument Flight Rules
The set of rules governing flight when the pilot relies primarily on instruments rather than visual reference. IFR flight requires an instrument rating and, in controlled airspace, an ATC clearance.
Instrument Landing System
A precision radio navigation system providing lateral (localiser) and vertical (glideslope) guidance to a runway threshold. ILS approaches are the standard precision approach type at major airports worldwide.
Instrument Meteorological Conditions
Weather conditions below the minima specified for visual flight rules, meaning the pilot cannot safely navigate by outside visual reference. Flying in IMC requires a valid instrument rating.
Instrument Rating
A rating added to a pilot licence that authorises flight under instrument flight rules, in cloud and reduced visibility. An IR is essential for commercial and airline operations and is required for the frozen ATPL.
International Standard Atmosphere
A defined model of standard atmospheric conditions used as a reference for aircraft performance calculations. ISA specifies a sea-level pressure of 1013.25 hPa and a sea-level temperature of 15 degrees Celsius.
Light Aircraft Pilot Licence
An EASA licence permitting flight of light aircraft with a maximum take-off mass up to 2,000 kg and up to three passengers. The LAPL has lower entry requirements than the PPL and privileges limited to specific aircraft categories.
A specific knowledge statement published by EASA that defines exactly what a student must understand in each ATPL subject. ATOs and study tools align content to learning objectives to ensure complete syllabus coverage.
The ratio of an aircraft's true airspeed to the local speed of sound. Above roughly Mach 0.75, compressibility effects become significant for most jet aircraft, and high-speed limits are often expressed in Mach.
The angular difference between true north and magnetic north at a given location. Pilots must apply variation to convert between true and magnetic headings and bearings.
Multi-Crew Cooperation
A course that trains pilots to operate as part of a two-person flight crew in a flight simulator. MCC is required before flying a multi-crew aircraft type and bridges the gap between single-pilot training and airline operations.
Meteorological Aerodrome Report
A standardised routine weather observation issued at regular intervals from an aerodrome, containing wind direction and speed, visibility, weather phenomena, cloud layers, temperature, dew point and altimeter setting. METARs are the primary weather product for pre-flight and in-flight planning.
Multi-Crew Pilot Licence
An EASA licence that trains a pilot from ab initio directly into multi-crew jet operations, typically in partnership with a specific airline. MPL replaces the separate PPL, CPL and IR steps with a competency-based programme focused on airline flying.
Maximum Take-Off Weight
The maximum mass at which the manufacturer certifies the aircraft to take off. Exceeding MTOW reduces structural margins and is not permitted; performance calculations reference MTOW and the actual take-off mass.
A rating that qualifies a pilot to fly aircraft with more than one engine, including procedures for handling an engine failure. It is a core step toward airliners, which are all multi-engine aircraft.
Non-Directional Beacon
A ground-based radio transmitter operating in the low to medium frequency band. An aircraft's ADF receiver detects the bearing to an NDB, used for general navigation and non-precision instrument approaches.
Notice to Air Missions
An official notice distributed to pilots containing information about changes or hazards essential for safe flight, such as runway closures, airspace restrictions, navigation aid outages or temporary obstacles.
The EASA regulation that sets out the requirements for pilot licences, ratings and certificates. Part-FCL defines the training, examinations and flight experience needed for each licence from PPL to full ATPL.
The EASA regulation governing medical requirements for pilots, including the standards for Class 1, Class 2 and LAPL medical certificates and the roles of AeMCs and AMEs.
The revenue-earning load carried by an aircraft: passengers, baggage and cargo. Payload is constrained by structural limits, fuel load and the aircraft's zero-fuel weight limit.
Private Pilot Licence
The entry-level pilot licence that allows the holder to fly a single-engine aircraft and carry passengers, but not for payment. The PPL is the foundation on which all further commercial training is built.
The atmospheric pressure setting that causes the altimeter to read zero when the aircraft is at the aerodrome reference point. QFE gives height above the aerodrome field directly from the instrument.
The altimeter indication obtained when the subscale is set to the standard datum of 1013.25 hPa. QNE gives flight levels used for vertical separation above the transition altitude.
The pressure setting that causes the altimeter to read altitude above mean sea level at the aerodrome reference point. QNH is the standard setting used below the transition altitude and for approach and landing.
A line of constant heading that crosses all meridians at the same angle. A rhumb line is simpler to fly than a great circle (constant heading throughout) but is not the shortest route on a sphere for long distances.
Area Navigation
A navigation method allowing an aircraft to follow any desired flight path, not only routes defined by ground-based radio beacons. Modern RNAV uses GNSS, DME and flight management system data to provide flexible, precise routing.
Single-Engine Piston
A class rating that authorises the holder to fly single-engine piston-engined aircraft. The SEP rating is typically the first rating added to a PPL and requires periodic revalidation.
The process by which ATC ensures that aircraft in controlled airspace maintain safe distances from each other and from terrain. Separation standards are specified as minimum horizontal and vertical distances.
A formal flight test conducted by an authority-approved examiner to assess whether a student meets the standard required for a licence or rating. Passing a skill test is the final gate before a licence or rating is issued.
A special NOTAM format reporting the condition of a runway affected by snow, slush, ice or standing water. SNOWTAMs are critical for winter operations because surface contamination directly affects take-off and landing performance.
The four-digit transponder code assigned by ATC, allowing the aircraft to be identified on radar. Special codes include 7700 for emergency, 7600 for radio failure and 7500 for unlawful interference.
A condition in which the wing exceeds its critical angle of attack and loses lift abruptly. Stalls can occur at any airspeed or attitude and are recovered by reducing angle of attack and applying power.
Terminal Aerodrome Forecast
A meteorological forecast for conditions at and around an aerodrome, normally valid for 9 or 24 hours. TAFs use the same coding format as METARs and are a standard document for pre-flight planning.
True Airspeed
The actual speed of an aircraft through the air mass, accounting for air density. TAS is higher than IAS at altitude because the air is less dense, and it is used for navigation calculations and fuel planning.
Terminal Manoeuvring Area
Controlled airspace at the convergence of ATS routes around major aerodromes. Aircraft entering or leaving the airspace of large airports transit through a TMA where separation services are provided.
The actual path of an aircraft over the ground, measured in degrees from north. Track is equal to heading adjusted for the drift caused by the wind.
The altitude at or below which vertical position is expressed as an altitude using QNH. Above the transition altitude, vertical position is expressed as a flight level using standard pressure. The value varies by country and aerodrome.
A qualification certifying a pilot to operate a specific aircraft type, such as a jet airliner. A type rating requires simulator and aircraft training followed by a skill test.
Takeoff decision speed. At V1 the pilot must be committed to continuing the take-off; any decision to reject must be made before this speed is reached. V1 is calculated for each departure based on runway length, aircraft mass and conditions.
Takeoff safety speed. V2 is the minimum safe airspeed at screen height following an engine failure after V1. Aircraft are certified to maintain a specified climb gradient at V2 with one engine inoperative.
Visual Flight Rules
The set of rules under which a pilot navigates primarily by visual reference to the ground and horizon. VFR requires minimum visibility and cloud clearance standards; flight into IMC on VFR is not permitted.
The greatest distance at which an object of known characteristics can be seen and identified. Visibility is reported in METARs and TAFs and determines whether VFR or IFR minima apply.
Visual Meteorological Conditions
Weather conditions equal to or better than the minima specified for visual flight rules. When conditions deteriorate below VMC minima, flight must be conducted under IFR.
Never-exceed speed. Vne is the maximum safe airspeed for an aircraft, beyond which structural damage may occur. It is marked by a red line on the airspeed indicator.
VHF Omnidirectional Range
A short-range radio navigation system providing bearing information from a ground station. VORs are widely used as en-route waypoints and are often co-located with DME to provide both bearing and distance.
Rotation speed. VR is the speed at which the pilot applies back pressure to lift the nose during take-off, allowing the aircraft to become airborne.
Best rate of climb speed. At Vy the aircraft achieves the greatest gain in altitude per unit of time. It is used after take-off to reach a safe altitude in the minimum time.
The definitions above are simplified for learning and should not be used as operational or legal references. Rules, standards and procedures change. Always confirm the details that matter for your training or operations with your ATO, your national aviation authority, and the published EASA and ICAO documentation. The METAR and TAF decoder and NOTAM decoder on this site can help you read real reports against the definitions here, but they are study tools, not operational tools.
METAR stands for Meteorological Aerodrome Report. It is a standardised routine weather observation issued at regular intervals from an aerodrome, containing wind direction and speed, visibility, weather phenomena, cloud cover, temperature, dew point and the altimeter setting. Pilots use METARs for pre-flight planning and in-flight weather awareness. You can decode a METAR automatically with the SkyStudy METAR and TAF decoder.
VFR (Visual Flight Rules) means the pilot navigates primarily by visual reference to the ground and horizon, and requires minimum visibility and cloud clearance to be maintained. IFR (Instrument Flight Rules) means the pilot operates by reference to cockpit instruments and does not rely on outside visual reference. IFR requires an instrument rating and, in controlled airspace, an ATC clearance. When weather deteriorates below VFR minima, the conditions are called IMC and flight must be conducted under IFR.
IMC stands for Instrument Meteorological Conditions. It describes weather conditions that are below the minima required to fly under Visual Flight Rules: visibility is too low, cloud is too close, or both. A pilot in IMC must have a valid instrument rating and fly under IFR. Operating in IMC without an instrument rating is illegal and extremely dangerous.
A frozen ATPL is not a separate licence. It describes the stage where a pilot holds a Commercial Pilot Licence (CPL), a multi-engine instrument rating, and a full set of ATPL theoretical knowledge passes, but has not yet accumulated the total flight experience required for the full ATPL. The holder can fly as a first officer in commercial operations. Once the required experience is met, the ATPL unfreezes to a full licence, which opens the path to command.
QNH is the atmospheric pressure setting that causes an altimeter to indicate altitude above mean sea level. Pilots set QNH on the altimeter subscale when operating below the transition altitude, so the instrument reads their true elevation above sea level. It is the standard setting for departures, arrivals and low-level flight. Above the transition altitude, pilots switch to the standard pressure of 1013.25 hPa, which gives flight levels.
SkyStudy covers all 14 ATPL subjects with exam-style questions, spaced repetition and timed mock exams. Every subject in the glossary has its own question set: from Meteorology and Radio Navigation to Air Law and Principles of Flight. Free to start, no card needed.
This page is general educational information for student pilots and may be out of date. Aviation rules, training requirements, costs, medical standards, and exam details change over time and vary by country, authority, and training organisation, so details here may no longer be current or may differ in your case. Always confirm the current details with your approved training organisation (ATO) and national aviation authority before relying on them. SkyStudy is an independent study aid, is not affiliated with EASA or any aviation authority, and does not guarantee any exam or licence outcome.Last reviewed June 2026.