The terms come from the videos on this site: we went through their transcripts and picked the words that come up most, then added the investigation terms used in our guides.
Each entry has a short definition, the events on this site whose videos use the term, and a link where there is more to read. Definitions follow the official sources, chiefly the FAA’s Pilot/Controller Glossary and ICAO’s rules for accident investigation, but are written for readers who do not fly. To choose a video to watch, see Where to Watch Air Crash Documentaries.
A
Accident
In the international rules, an occurrence linked to a flight in which someone is killed or seriously injured, the aircraft is badly damaged or suffers structural failure, or the aircraft goes missing. Less serious events are classed as incidents or serious incidents.
Accredited representative
The person a country appoints to take part in another country’s accident investigation, under ICAO Annex 13. The countries where the aircraft was registered, designed and built, and where the airline is based, each have this right. See Who Investigates Plane Crashes?
Active failure
An unsafe act by someone at the sharp end, such as a pilot, controller or mechanic, whose effect shows up almost at once. Compare latent condition.
ADS-B
Automatic Dependent Surveillance–Broadcast. The aircraft works out its own position by satellite and broadcasts it, so controllers and other aircraft can see it. Investigators use ADS-B data to draw flight paths.
Aileron
A hinged surface on the back of each wing, near the tip. The ailerons move in opposite directions to roll the aircraft into a bank.
Airworthiness directive (AD)
A legally binding order from an aviation regulator, such as the FAA, requiring owners to inspect, repair or modify an aircraft to fix a known unsafe condition.
Heard in: Helios Airways Flight 522, American Airlines Flight 587.
Alternate airport
An airport, chosen before departure, where a flight can land if it cannot land at its destination. Flights must carry enough fuel to reach it.
Heard in: Jet Airways Flight 555, where the crew diverted to their alternate in poor visibility and landed with very little fuel.
Altimeter
The instrument that shows the aircraft’s height. A barometric altimeter measures air pressure and must be set to the local pressure to read correctly near the ground; a radio altimeter measures height above the ground directly.
Heard in: Air Niugini Flight 73, Olympic Airways Flight 411, Air Canada Flight 143.
Angle of attack
The angle between the wing and the oncoming air. Lift rises with angle of attack up to a critical point; beyond it the wing stalls.
Annex 13
The part of the international aviation rules, maintained by ICAO, that governs accident investigation. It says the country where an accident happens leads the investigation and that the sole aim is prevention, not blame. See How Plane Crash Investigations Work.
Approach control
The air traffic control unit that handles aircraft arriving at and leaving a busy airport area, between the en-route centre and the tower.
Heard in: Delta Air Lines Flight 191, Delta Air Lines Flight 1080.
APU
Auxiliary power unit. A small turbine engine, usually in the tail, that supplies electricity and compressed air when the main engines are not running.
Heard in: Swissair Flight 551, Eastern Air Lines Flight 855, Jet Airways Flight 555.
ATC
Air traffic control. The service, run by controllers on the ground, that keeps aircraft safely separated and gives them clearances and instructions by radio. “ATC” is also used for the controllers themselves.
Heard in: almost every video on this site.
Autopilot
The system that flies the aircraft automatically, holding a heading, altitude or programmed route. It does exactly what it is set to do, which is why an aircraft with an incapacitated crew can fly on for hours.
Heard in: Helios Airways Flight 522, Swissair Flight 111, Air Niugini Flight 73.
Autothrottle
The system that sets engine power automatically to hold a selected speed. Airbus calls it autothrust.
B
Bag matching
The rule that a checked bag does not travel unless the passenger who checked it is on board. Tightened after the bombing of Pan Am Flight 103. See What Changed After Pan Am 103.
Bank angle
How far the aircraft is tilted, or rolled, to one side, measured in degrees.
Heard in: Jet Airways Flight 555, Air Canada Flight 143, Swissair Flight 111.
Bird strike
A collision between an aircraft and a bird. Most do little harm, but birds swallowed by an engine can damage or stop it. See Bird Strikes.
Black box
The popular name for the two flight recorders, the cockpit voice recorder and the flight data recorder. They are painted bright orange or yellow so they can be found. See Black Boxes Explained.
Bleed air
Hot, compressed air taken from the engines’ compressors and used to pressurise and heat the cabin, among other jobs.
Heard in: Helios Airways Flight 522, TWA Flight 800.
Brace position
The posture passengers are told to adopt before an emergency landing, bent forward with the head protected, to reduce injuries on impact. The crew command is often simply “Brace, brace”.
Heard in: Air Canada Flight 143, Eastern Air Lines Flight 855.
Bulkhead
A wall across the fuselage. The pressure bulkhead at the rear of the cabin is a dome that holds in the cabin pressure.
C
Cabin altitude
The altitude that matches the air pressure inside the cabin. At cruise, an airliner keeps its cabin at the equivalent of a few thousand feet, however high it flies. If the cabin altitude climbs too high, a warning sounds.
Heard in: Helios Airways Flight 522, where the cabin never pressurised.
Cabin crew
The flight attendants. Their main job is safety: briefing passengers, handling emergencies in the cabin and running an evacuation.
Captain
The pilot in command, who has final authority over the flight. Usually sits in the left seat.
Cargo door
The door to the cargo hold below the cabin. Several accidents have been caused by cargo doors opening in flight, because the cabin pressure behind them is high. See DC-10 Crashes.
Cause not established
What we write on an event page when the official investigation could not determine a cause. Theories, if any, are kept in a separate section. See How We Check Facts.
Centre wing tank
A fuel tank in the structure that joins the two wings, under the cabin. On TWA Flight 800 the nearly empty centre tank of a Boeing 747 exploded, and the investigation led to fuel tank inerting.
CFIT (controlled flight into terrain)
An accident in which a working aircraft, under the crew’s control, is flown into the ground, water or an obstacle, usually because the crew did not know how close it was. See Controlled Flight Into Terrain.
Checklist
A written list of steps the crew reads and checks, for normal phases of flight and for emergencies. Missed checklist items appear in many accident reports.
Heard in: Swissair Flight 551, Helios Airways Flight 522, Air Canada Flight 143, Eastern Air Lines Flight 855.
Chip detector
A magnetic plug in an engine’s oil system that catches metal particles, an early sign of wear. On Eastern Air Lines Flight 855, chip detectors fitted without their O-ring seals let the oil leak from all three engines. See Plane Crashes Caused by Maintenance Errors.
Circuit breaker
A switch that cuts power to a circuit when it overloads, and can be pulled or reset by hand.
Heard in: Swissair Flight 111; Air Canada Flight 143, where pulling and resetting a breaker left the fuel gauges blank.
Cockpit voice recorder (CVR)
The flight recorder that records the pilots’ voices, radio calls and sounds in the cockpit. Older units kept 30 minutes or two hours; new large aircraft must keep 25 hours. See Black Boxes Explained.
Heard in: Helios Airways Flight 522, TWA Flight 800, Delta Air Lines Flight 191.
Composite
A material made of fibres, such as carbon, set in resin. Strong and light, it is used for tails, wings and fuselages. The tail fin of American Airlines Flight 587 was made of composite.
Contributing factor
A condition that made an accident more likely or worse, without being its main cause. NTSB reports list them after the probable cause.
Corrosion
The slow chemical attack of metal, such as rust on steel or oxidation on aluminium. Salt air speeds it up.
Heard in: Aloha Airlines Flight 243.
CRM (crew resource management)
Training that teaches crews to communicate, share the workload and challenge each other, including a captain, when something looks wrong. See What Changed After Tenerife.
Heard in: the Tenerife airport disaster, Air Niugini Flight 73, Swissair Flight 111.
Crossfeed
A valve that lets fuel from one wing’s tanks feed the engine on the other side, to balance the fuel. On Air Transat Flight 236, opening the crossfeed sent the remaining fuel to the leaking engine.
Cumulonimbus
A towering thunderstorm cloud. It can produce lightning, hail, heavy rain, severe turbulence and microbursts.
Heard in: Delta Air Lines Flight 191.
D
Decision height
On a precision approach such as an ILS, the height at which the pilots must see the runway environment to continue. If they cannot, they must go around.
Heard in: Jet Airways Flight 555.
Decompression
A loss of cabin pressure. It can be explosive, rapid or gradual, depending on how fast the pressure escapes. See Explosive vs Rapid Decompression.
Heard in: Aloha Airlines Flight 243, Helios Airways Flight 522.
De-icing
Removing ice, frost or snow from an aircraft before take-off, usually by spraying heated fluid. Anti-icing fluid is then used to stop new ice forming for a limited time. See Aircraft Icing.
Dispatch
The airline function that plans a flight and releases it to fly, checking fuel, weather, routes and the aircraft’s condition. In many airlines a licensed dispatcher shares responsibility with the captain.
Ditching
A planned emergency landing on water. Crews prepare the cabin, brief passengers on life vests and aim to touch down as slowly and level as possible.
Heard in: Eastern Air Lines Flight 855, whose crew prepared to ditch before an engine restarted.
Downdraft
A column of air moving downward, especially under a thunderstorm. A strong, small downdraft that spreads out at the ground is a microburst.
Heard in: Delta Air Lines Flight 191.
Dripstick
A rod lowered into a fuel tank from underneath to measure the fuel level by hand, used when the gauges do not work.
Heard in: Air Canada Flight 143, the Gimli Glider, where dripstick readings were converted with the wrong factor.
Duty time
The time a crew member is on duty, limited by law to manage fatigue. Pressure from new duty-time limits was a factor in the Tenerife collision.
Heard in: the Tenerife airport disaster.
E
ECAM and EICAS
The screens that show engine readings and system warnings, with the actions to take. Airbus calls its system ECAM (Electronic Centralised Aircraft Monitor). Boeing’s is EICAS (Engine Indicating and Crew Alerting System).
Heard in: Air Transat Flight 236.
EGPWS
Enhanced Ground Proximity Warning System. It adds a worldwide terrain database to the older GPWS, so it can warn of high ground ahead, not just below. Calls include “Terrain, terrain” and “Pull up”. See TCAS and Terrain Warnings.
Heard in: Air Niugini Flight 73, whose crew continued an approach through repeated EGPWS alerts.
Elevator
The hinged surface on the horizontal tail that raises or lowers the nose.
Heard in: Emery Worldwide Flight 17; Delta Air Lines Flight 1080, where a jammed elevator was overcome with engine thrust.
Engine failure
The loss of power from an engine. Airliners are designed and certified to take off and climb safely with one engine failed. Olympic Airways Flight 411 lost an engine as it lifted off from Athens.
Evacuation slide
An inflatable slide that deploys from an exit so passengers can leave quickly. Slides at a raised tail can be too short, as on the Gimli Glider.
Heard in: Air Canada Flight 143, Aloha Airlines Flight 243.
F
Fatal accident
An accident in which at least one person dies. It does not mean everyone on board died. See Deadliest Plane Crashes by Decade.
Fatality risk
IATA’s measure of how exposed a passenger or crew member is to an accident with no survivors, independent of aircraft size. See Is Flying Safe?
Final approach
The last part of an approach, lined up with the runway and descending towards it.
Final report
The investigating body’s full, published account of an accident: facts, analysis, conclusions and safety recommendations. See How to Read an Air Accident Final Report.
Findings
The numbered conclusions at the end of a final report. Some explain the accident; others record facts that were established.
First officer
The second pilot, also called the co-pilot. Usually sits in the right seat and shares the flying with the captain.
Flameout
When the flame in a jet engine’s combustion chamber goes out and the engine stops producing power, for example from lack of fuel. Both engines of Helios Airways Flight 522 flamed out when its fuel ran out.
Flaps
Panels that extend from the back of the wings to give more lift at low speed, for take-off and landing. Flaps are set in stages.
Flare
The gentle raising of the nose just before touchdown, to slow the descent.
Flight data recorder (FDR)
The flight recorder that stores measurements such as altitude, speed, heading, control positions and engine settings. New aircraft must record at least 88 parameters. See Black Boxes Explained.
Heard in: Emery Worldwide Flight 17, Swissair Flight 111, American Airlines Flight 587.
Flight engineer
The third crew member on older airliners such as the Boeing 747-100 and the L-1011, who managed the engines, fuel and systems. Modern airliners are flown by two pilots.
Heard in: Olympic Airways Flight 411, Eastern Air Lines Flight 855, Delta Air Lines Flight 1080.
Flight level
An altitude based on a standard pressure setting, given in hundreds of feet. Flight level 350 is 35,000 feet.
Heard in: the Tenerife airport disaster, Air Niugini Flight 73, Eastern Air Lines Flight 855.
Fuel exhaustion
Running out of usable fuel. Compare fuel starvation. See Planes That Ran Out of Fuel.
Fuel starvation
When there is fuel on board but it cannot reach the engines, for example because a valve is set wrongly.
Heard in: Air Transat Flight 236, Jet Airways Flight 555.
Fuselage
The main body of the aircraft, holding the cockpit, cabin and cargo holds.
G
Glide ratio
How far an aircraft travels forward for each unit of height it loses with no engine power. Airliners glide surprisingly well, as the Gimli Glider and Air Transat Flight 236 showed.
Glide slope
The vertical part of an ILS: a radio beam that guides the aircraft down a steady descent path to the runway, usually about 3 degrees.
Heard in: Air Niugini Flight 73, Delta Air Lines Flight 191.
Go-around
Abandoning a landing and climbing away to try again or divert. Always an option, and often the safe one.
Heard in: Air Niugini Flight 73, Delta Air Lines Flight 191, Jet Airways Flight 555.
Go-team
The NTSB’s name for the investigators it sends to a major accident site. See How Plane Crash Investigations Work.
GPWS
Ground Proximity Warning System. Uses the radio altimeter to warn when the aircraft is too close to the ground or descending towards it too fast. Replaced on airliners by EGPWS.
H
Headwind and tailwind
Wind blowing against the aircraft (headwind) or from behind (tailwind). Taking off and landing into a headwind shortens the run. In a microburst, a headwind that suddenly becomes a tailwind costs the aircraft airspeed.
Heard in: Delta Air Lines Flight 191.
Holding pattern
A racetrack-shaped pattern an aircraft flies over a fixed point while it waits.
Heard in: Helios Airways Flight 522, which circled in a hold near Athens on autopilot.
Hydraulics
Systems that use fluid under pressure to move the flight controls, landing gear and brakes on large aircraft.
Heard in: Air Transat Flight 236, Air Canada Flight 143.
Hypoxia
A lack of oxygen reaching the body’s tissues. At high altitude it impairs judgement within moments and leads to unconsciousness, often without the person noticing. See Explosive vs Rapid Decompression.
Heard in: Helios Airways Flight 522.
I
Icing
Ice forming on an aircraft, especially on the wings, which spoils the airflow and reduces lift. See Aircraft Icing.
ILS (instrument landing system)
A ground radio system that guides aircraft to the runway in poor visibility, with a localizer for direction and a glide slope for descent.
Heard in: Air Niugini Flight 73, Jet Airways Flight 555.
Indicated airspeed
The airspeed shown on the instrument, measured from the pressure of the air rushing in. It is what the wing “feels”, so pilots fly by it.
Heard in: Delta Air Lines Flight 191.
Inerting
Filling the empty space in a fuel tank with nitrogen-enriched air, so there is too little oxygen for the fuel vapour to ignite. Required after the TWA Flight 800 investigation. See In-Flight Fire Accidents.
Heard in: TWA Flight 800.
Interim statement
A public update that an investigating body must publish on each anniversary of an accident if its final report is not yet out.
K
Knots
Nautical miles per hour, the unit of speed in aviation. One knot is 1.852 kilometres per hour, or about 1.15 miles per hour.
L
Lap joint
A seam where two fuselage skin panels overlap and are joined. On Aloha Airlines Flight 243, fatigue cracks along a lap joint linked up and part of the roof tore away.
Latent condition
A weakness built into a system by earlier decisions, such as a confusing design or a missing procedure, that lies dormant until an active failure exposes it. See The Swiss Cheese Model.
Localizer
The part of an ILS that gives left-right guidance to the runway centreline.
Loss of control
When the crew can no longer keep the aircraft in the attitude or flight path they intend, for example after a stall, an upset or a control failure.
M
Mach
Speed as a fraction of the speed of sound. Airliners cruise at about Mach 0.8.
Master caution
A light in front of each pilot that comes on to draw attention to a fault shown elsewhere. A red master warning is for more urgent problems.
Heard in: Helios Airways Flight 522.
Mayday
The international distress call, spoken three times, for a situation that threatens the aircraft or lives. It gets the flight priority over everyone else. Compare pan-pan.
Heard in: Air Transat Flight 236, Helios Airways Flight 522, Aloha Airlines Flight 243.
MCAS
Maneuvering Characteristics Augmentation System, flight control software on the Boeing 737 MAX that could move the tail’s stabiliser to push the nose down. It is central to the investigations of the 737 MAX crashes in 2018 and 2019. See Boeing 737 MAX Timeline.
Metal fatigue
Cracking caused by repeated loads that are each well below the metal’s breaking strength, such as the pressurisation of a fuselage on every flight. See Aloha 243 and the Aging Aircraft Rules.
Heard in: Aloha Airlines Flight 243.
Microburst
A small, intense downdraft from a thunderstorm that spreads out when it hits the ground. An aircraft flying through one meets a headwind, then a downdraft, then a tailwind. See Wind Shear and Microbursts.
Heard in: Delta Air Lines Flight 191.
Mid-air collision
A collision between two aircraft in flight. See Mid-Air Collisions.
Minimum descent altitude (MDA)
On an approach without vertical guidance, the lowest altitude the aircraft may descend to unless the pilots can see the runway.
Heard in: Air Niugini Flight 73, Emery Worldwide Flight 17.
Minimum equipment list (MEL)
The approved list of equipment an aircraft may fly without, and on what conditions. On the Gimli Glider, the list did not allow the aircraft to fly with blank fuel gauges.
Heard in: Air Canada Flight 143.
Minimum fuel
A call telling air traffic control that the flight can accept little or no delay. It is not yet an emergency; if fuel falls further, the crew declares one with “Mayday fuel”.
Heard in: Jet Airways Flight 555.
Missed approach
The published procedure for climbing away when a landing cannot be completed. Flying it is a go-around.
Heard in: Air Niugini Flight 73, Jet Airways Flight 555.
N
NTSB
The National Transportation Safety Board, the independent US agency that investigates civil aviation accidents and major accidents in other modes of transport. See Who Investigates Plane Crashes?
O
O-ring
A rubber ring that seals a joint against leaks. Missing O-rings caused all three engines on Eastern Air Lines Flight 855 to lose their oil.
Heard in: Eastern Air Lines Flight 855.
Outflow valve
A valve that lets air out of the cabin at a controlled rate, which is how the pressurisation system controls cabin pressure.
Heard in: Helios Airways Flight 522.
Oxygen masks
Passenger masks drop automatically if the cabin altitude climbs too high, at about 14,000 feet. Pilots have their own quick-donning masks, which they must put on first.
Heard in: Helios Airways Flight 522.
P
Packs
The air conditioning units that cool and supply the pressurised air to the cabin. On TWA Flight 800, packs under the centre fuel tank heated it while the aircraft waited on the ground.
Heard in: Helios Airways Flight 522, TWA Flight 800.
Pan-pan
The urgency call, one level below a Mayday, used when there is a problem but no immediate danger.
Heard in: Swissair Flight 111, whose crew made a pan-pan call after they noticed smoke in the cockpit.
Party system
The NTSB’s practice of inviting organisations with expertise, such as the manufacturer, the airline and the pilots’ union, to help with an investigation. Only the NTSB writes the conclusions.
Pitch
The nose-up or nose-down attitude of the aircraft, controlled by the elevator.
Pitot tube
A small forward-facing tube that measures the pressure of the oncoming air, from which airspeed is worked out. If it is blocked, by ice for example, the airspeed reading is wrong.
Preliminary report
A first report of basic facts, due within 30 days of an accident under ICAO rules. It rarely gives a cause.
Pressurisation
Pumping air into the cabin so that the pressure inside stays close to that at a low altitude while the aircraft flies high.
Heard in: Helios Airways Flight 522.
Primary and secondary radar
Primary radar detects aircraft from radio echoes off their structure. Secondary radar receives the replies from the aircraft’s transponder, which add its identity and altitude.
Heard in: Air Canada Flight 143, Air Transat Flight 236.
Probable cause
The NTSB’s formal statement of the main reason an accident happened, determined after weighing all the evidence. See How to Read an Air Accident Final Report. Where a finding is disputed, see Plane Crashes With Disputed Causes.
Heard in: Aloha Airlines Flight 243, American Airlines Flight 587.
Q
QRH (quick reference handbook)
A book of checklists for abnormal and emergency situations, kept in the cockpit.
Heard in: Air Transat Flight 236.
R
Ram air turbine (RAT)
A small propeller that drops out of the aircraft into the airflow when the engines have stopped, driving a pump or generator to power essential controls.
Heard in: Air Canada Flight 143, Air Transat Flight 236.
Rejected take-off
Stopping a take-off on the runway after it has begun. Below V1 the crew can stop; above it they continue.
Rudder
The hinged surface on the fin that swings the nose left or right (yaw).
Heard in: American Airlines Flight 587, where repeated full rudder inputs overloaded the fin until it broke off.
Runway incursion
The incorrect presence of an aircraft, vehicle or person on a runway that is in use. See Runway Incursions.
Runway visual range (RVR)
The distance a pilot can see along the runway, measured by instruments. Approaches have minimum RVR values.
Heard in: Jet Airways Flight 555.
S
Safety recommendation
A formal proposal from an investigating body to a regulator, manufacturer or airline to fix a safety problem. It is not binding.
Sideslip
Flying with the controls crossed so the aircraft moves slightly sideways through the air. It adds drag, so the aircraft can lose height without gaining speed.
Heard in: Air Canada Flight 143, where Captain Pearson used a sideslip to lose height before landing at Gimli.
Slats
Panels that extend from the front of the wings to give more lift at low speed, working with the flaps.
Spatial disorientation
When a pilot’s senses give a false picture of the aircraft’s attitude, for example in cloud or at night, and the instruments are not believed.
Spoilers
Panels on top of the wings that rise to reduce lift and add drag, used to descend faster or to slow down on the runway.
Squawk
The four-digit code set on the transponder. Some codes have fixed meanings: 7700 for an emergency, 7600 for radio failure and 7500 for unlawful interference.
Stabilised approach
An approach on the right path, at the right speed and with the aircraft configured for landing by a set height. If it is not stabilised by then, airline rules say go around.
Stall
When the wing exceeds its critical angle of attack and loses lift. It has nothing to do with the engines.
Heard in: Delta Air Lines Flight 1080, Olympic Airways Flight 411.
Stick shaker
A motor that shakes the control column to warn the pilots that the aircraft is close to a stall.
Heard in: Delta Air Lines Flight 191.
Swiss cheese model
James Reason’s picture of how accidents happen: several layers of defence, each with holes, which must all line up. See The Swiss Cheese Model.
T
Take-off clearance
Air traffic control’s permission to take off. Since the Tenerife collision, controllers and pilots use the word “take-off” only when a take-off clearance is given or cancelled.
Heard in: the Tenerife airport disaster.
Take-off configuration warning
A horn that sounds if the pilots set take-off power when the aircraft is not set up for take-off, for example with the flaps up. On the Boeing 737 the same horn was used for the cabin altitude warning, which confused the Helios 522 crew.
Heard in: Helios Airways Flight 522.
TCAS
Traffic Collision Avoidance System. It detects nearby aircraft by their transponders and, if a collision threatens, tells the pilots to climb or descend. See TCAS and Terrain Warnings.
Tower
The air traffic controllers in the airport’s control tower, responsible for the runways and the air close to the airport.
Heard in: the Tenerife airport disaster, American Airlines Flight 587, Air Transat Flight 236.
Transponder
A radio on the aircraft that answers secondary radar with a code (squawk) and the aircraft’s altitude.
Heard in: Air Canada Flight 143, Helios Airways Flight 522, Swissair Flight 111.
Trijet
An airliner with three engines, such as the Lockheed L-1011 TriStar, the McDonnell Douglas DC-10 and the MD-11. See Lockheed L-1011 TriStar Crashes.
Trim
A small adjustment that holds a control surface in position so the pilot does not have to keep pressure on the controls.
Heard in: Delta Air Lines Flight 1080, Air Transat Flight 236.
Type rating
The qualification a pilot needs to fly a particular large aircraft type, such as the Boeing 737.
U
Underwater locator beacon
A small device on each flight recorder that sends out pings when it is under water, so searchers can find it. See Black Boxes Explained.
UTC
Coordinated Universal Time, also called Zulu time. Accident reports often give times in UTC, so check the time zone before comparing them with local times.
V
V1, VR and V2
Take-off speeds worked out for each flight. V1 is the decision speed: after it, the crew continues the take-off even if an engine fails. VR is the speed at which the pilot rotates, or lifts the nose. V2 is the safe climb speed with one engine failed.
Heard in: Emery Worldwide Flight 17, Olympic Airways Flight 411.
Vectors
Headings given by air traffic control to steer an aircraft, for example onto an approach.
Heard in: Swissair Flight 111, Eastern Air Lines Flight 855.
Vertical speed
How fast the aircraft is climbing or descending, usually in feet per minute.
Vertical stabilizer
The fixed fin on top of the tail, which keeps the aircraft pointing straight. The rudder is hinged to its back edge.
Heard in: American Airlines Flight 587.
Visibility
How far you can see horizontally. Every approach has a minimum visibility below which the crew may not continue.
Heard in: Emery Worldwide Flight 17, Jet Airways Flight 555, the Tenerife airport disaster.
W
Wake turbulence
The swirling air left behind an aircraft, mainly two vortices trailing from the wingtips. Controllers space aircraft to let it die away.
Heard in: American Airlines Flight 587, which met the wake of a Boeing 747 that had departed ahead.
Wide-body
An airliner with two aisles, such as the Boeing 747, the L-1011 or the Airbus A330. See Boeing 747 Crashes.
Wind shear
A sudden change in wind speed or direction over a short distance. Near the ground, it can rob an aircraft of airspeed and height. See Wind Shear and Microbursts.
Heard in: Delta Air Lines Flight 191.
Sources
- FAA, Pilot/Controller Glossary (effective 9 July 2026).
- FAA, Pilot’s Handbook of Aeronautical Knowledge.
- ICAO Annex 13 provisions, Uniting Aviation (ICAO), 30 August 2021.
- NTSB, Cockpit Voice Recorders and Flight Data Recorders.
- IATA, 2025 Safety Report press release, 9 March 2026 (fatality risk).
- The official reports cited on each linked event page.
How we choose and check our sources is set out in How We Choose Air Crash Videos and How We Check Facts.