583: The Tenerife airport disaster, which occurred on March 27, 1977, remains the accident with the highest number of airliner passenger fatalities. 583 people died when a KLM Boeing 747 attempted to take off without clearance, and collided with a taxiing Pan Am 747 at Los Rodeos Airport on the Canary Island of Tenerife, Spain. There were no survivors from the KLM aircraft; 61 of the 396 passengers and crew on the Pan Am aircraft survived. Pilot error was the primary cause, as the KLM captain began his takeoff run without obtaining air traffic control clearance. A contributing factor was the dense fog. The KLM flight crew could not see the Pan Am aircraft on the runway until immediately before the collision. The accident had a lasting influence on the industry, particularly in the area of communication. An increased emphasis was placed on using standardized phraseology in air traffic control (ATC) communication by both controllers and pilots alike. Furthermore, all members of the cabin crew are now able to question the captain's judgment concerning the safety of the airliner.
520: The crash of Japan Airlines Flight 123 on August 12, 1985, is the single-aircraft disaster with the highest number of fatalities: 520 people died on board a Boeing 747. The aircraft suffered an explosive decompression from an incorrectly repaired aft pressure bulkhead, which failed in mid flight, destroying most of its vertical stabilizer and severing all of the hydraulic lines, making the 747 virtually uncontrollable. Pilots were able to keep the plane flying for 32 minutes after the mechanical failure before crashing into a mountain. All 15 crew members and 505 of the 509 passengers on board died. The death toll was exacerbated by delays in the rescue operation. Although a number of people survived the impact, by the time the Japanese rescue teams arrived at the crash site all but four had succumbed to their injuries.
349: On November 12, 1996, the world's deadliest mid-air collision was the Charkhi Dadri mid-air collision involving Saudia Flight 763 and Kazakhstan Airlines Flight 1907 over Charkhi Dadri, India. The collision was mainly the result of the Kazakh pilot flying lower than the assigned clearance altitude. All 349 passengers and crew on board both aircraft died. The Ramesh Chandra Lahoti Commission, empowered to study the causes, recommended the creation of the "semi-circular rule", to prevent aircraft from flying in opposite directions at the same altitude. The Civil Aviation Authorities in India made it mandatory for all aircraft flying in and out of India to be equipped with a Traffic Collision Avoidance System (TCAS), setting a worldwide precedent for mandatory use of TCAS.
346: On March 3, 1974, Turkish Airlines Flight 981, a McDonnell Douglas DC-10, crashed in a forest northeast of Paris, France. The London-bound plane crashed shortly after taking off from Orly airport; all 346 people on board died. It was later determined that the cargo door detached, which caused an explosive decompression; this caused the floor just above to collapse. The collapsed floor severed the control cables, which left the pilots without control of the elevators, the rudder and No. 2 engine. The plane entered a steep dive and crashed. It was the deadliest plane crash of all time until the Tenerife disaster in 1977.
329: On June 23, 1985, Air India Flight 182, a Boeing 747-237B crashed off the southwest coast of Ireland when a bomb exploded in the cargo hold. All 307 passengers and 22 crew members died. One passenger had checked in as "M. Singh". Singh did not board the flight. However, his suitcase containing the bomb was loaded onto the plane. "Mr Singh" was never identified and captured. It was later determined Sikh extremists were behind the bombing as a retaliation for the Indian government's attack on the Golden Temple in the city of Amritsar, which is very important for the Sikhs. This was, at the time, the deadliest terrorist attack involving an airplane.
301: On August 19, 1980, Saudi Arabian Airlines Flight 163, a Lockheed L-1011 became the world's deadliest aviation accident that did not involve a crash. The crew performed an emergency landing at Riyadh after a fire broke out in an aft baggage compartment. The fire burned through the ceiling of the compartment and into the passenger cabin. While the crew managed to land the plane safely, the captain did not stop immediately and order an evacuation. He taxied off the runway instead, by which time everyone in the cabin had become unconscious due to fumes and unable to open any doors or evacuate. All 301 passengers and crew died of suffocation before rescue ground crews could open any door, after which the aircraft burst into flames and was consumed by fire.
298: On July 17, 2014, Malaysia Airlines Flight 17, a Boeing 777-200ER, flying from Amsterdam to Kuala Lumpur with 298 people on board, was shot down in an area of Eastern Ukraine near the Ukraine/Russian border. There were 283 passengers, including 3 infants, and 15 crew members on board MH17, all of whom perished. The crew were all Malaysian, while the passengers were of various nationalities, most from the Netherlands. According to a Dutch report, high-energy objects hit the plane in midair, causing it to break apart. According to the preliminary report of the international investigation commission, the plane was shot down most likely by Russian forces using a surface-to-air missile fired from the Ukrainian territory which they controlled. While the investigation is still ongoing, it has been determined beyond reasonable doubt that the missile launcher (which only the armed forces could possess) had been delivered from Russia and taken back to that country after MH17 had been shot down. This was the deadliest accident involving a Boeing 777.
290: On July 3, 1988, Iran Air Flight 655, an Iranian civilian airliner, was shot down by two surface-to-air missiles from the U.S. Navy's guided missile cruiser, USS Vincennes, over the Strait of Hormuz. All 290 passengers and crew aboard the Airbus A300B2-203 died.
275: On February 19, 2003, an Iranian military Ilyushin Il-76 crashed in mountainous terrain near Kerman in Iran. The official report says bad weather brought the aircraft down; high winds and fog were present at the time of the crash.
273: On May 25, 1979, American Airlines Flight 191, following improper maintenance, which caused the number one engine and pylon on the left wing to separate and flip over the top of the wing, a McDonnell Douglas DC-10-10, lost control and crashed near O'Hare International Airport in Des Plaines, Illinois. The crash resulted in the deaths of all 271 passengers and crew on board, as well as two people on the ground. It remains the deadliest commercial aircraft accident in United States history, and was also the country's deadliest aviation disaster until the September 11 attacks in 2001.
270: On December 21, 1988, Pan Am Flight 103, a Boeing 747–121 bound for New York-JFK from London-Heathrow with continued service to Detroit, was destroyed by a terrorist bomb over the town of Lockerbie, Scotland. All 243 passengers and 16 crew, and 11 people on the ground (all residents of Sherwood Crescent, Lockerbie), died, making it the worst terrorist attack involving an aircraft in the UK and the deadliest terrorist attack on British soil. Following the crash, the Federal Aviation Administration imposed new security measures on American airlines flying out of 103 airports in Western Europe and the Middle East.
269: On September 1, 1983, a Soviet interceptor Sukhoi Su-15 shot down Korean Air Lines Flight 007, a Boeing 747-230B, bound for Gimpo International Airport in Seoul, South Korea, after it flew into Soviet airspace; all 269 passengers and crew on board died.
265: On November 12, 2001, American Airlines Flight 587, an Airbus A300, crashed in the Belle Harbor neighborhood of Queens, New York, just after departing John F. Kennedy International Airport bound for Las Américas International Airport, Santo Domingo. The first officer's overuse of the rudder in response to wake turbulence from a Japan Airlines 747 was cited as cause. All 260 people on board, as well as five people on the ground, died from the crash. It is the second-deadliest aviation accident on U.S. soil, after American Airlines Flight 191.
264: On April 26, 1994, China Airlines Flight 140 was completing a routine flight and approach at Nagoya Airport, Japan, when the Airbus A300B4-622R's First Officer inadvertently pressed the Takeoff/Go-around button which raises the throttle position to the same as take offs and go-arounds. The action and the two pilots' reaction resulted in a crash that killed 264 (15 crew and 249 passengers) of the 271 people aboard.
261: On July 11, 1991, Nigeria Airways Flight 2120, a Douglas DC-8-61 aircraft operated by Nationair Canada, crashed in Jeddah, Saudi Arabia, after two tires ignited upon takeoff, leading to an in-flight fire. All 247 passengers and 14 crew members were killed. It is the deadliest aviation accident involving a DC-8, the largest aviation disaster involving a Canadian-registered aircraft and the second-worst accident in Saudi Arabia.
257: On November 28, 1979, Air New Zealand Flight 901, an Antarctic sightseeing flight, collided with Mount Erebus on Ross Island, Antarctica, killing all 237 passengers and 20 crew on board. The flight crew had not been informed that the computer coordinates for the flight path of the McDonnell Douglas DC-10-30 had been changed the night before, directing the flight directly into Mount Erebus rather than the usual path down McMurdo Sound.
256: On December 12, 1985, a Douglas DC-8, Arrow Air Flight 1285, carrying American military personnel on a charter flight home for Christmas, crashed in Newfoundland; all 248 passengers and 8 crew members died. The Canadian Aviation Safety Board investigating the cause of the crash issued two different reports: the majority report cited ice on the wings as cause of the crash; the minority report suggests an explosion was the likely cause.
239: On March 8, 2014, a Boeing 777-200ER, Malaysia Airlines Flight 370, flying from Kuala Lumpur, Malaysia, to Beijing, China, lost contact with air traffic controllers over the South China Sea, deviated from its planned route, and was presumed lost in the southern Indian Ocean. It carried 12 Malaysian crew members and 227 passengers from 15 nations. A multinational search effort, the most extensive and expensive in aviation history, has thus far failed to locate them, though debris from the aircraft were recovered on July 29, 2015, on Réunion Island. Numerous theories have been offered to explain the disappearance of the flight, but none has been confirmed.
234: On September 26, 1997, an Airbus A300B4-220, Garuda Indonesia Flight 152, which departed from Jakarta, Indonesia, and was preparing to land at Medan, North Sumatra, crashed into mountainous terrain, killing 222 passengers and 12 crew members. The causes included poor visibility and confusion by air traffic controllers.
230: On July 17, 1996, a Boeing 747-131, TWA Flight 800, carrying 212 passengers and 18 crew, exploded and crashed into the Atlantic Ocean near East Moriches, New York, shortly after departing from John F. Kennedy International Airport on a flight to Paris and Rome. A lengthy investigation concluded that the probable cause of the accident was a short circuit in a fuel tank that contained an explosive mixture of fuel and air vapor. As a result, new requirements were developed to prevent future fuel tank explosions in aircraft.
229: On September 2, 1998, a McDonnell Douglas MD-11, Swissair Flight 111, carrying 215 passengers and 14 crew from New York City to Geneva, Switzerland crashed into the Atlantic Ocean near Halifax, Nova Scotia, Canada, killing all aboard. After a lengthy investigation, an official report stated that flammable material used in the aircraft's structure, specifically the Personal TV Systems recently installed in the Business Class Cabin, allowed a fire to spread, resulting in a loss of control.
228: On June 1, 2009, an Airbus A330-203, Air France Flight 447, carrying 216 passengers and 12 crew, was en route from Rio de Janeiro, Brazil to Paris, France, when it crashed into the Atlantic Ocean. The aircraft's flight recorders were not recovered from the ocean floor until May 2011, and the final investigative report was released in July 2012. It determined that the disaster was likely due to the aircraft's pitot tubes being obstructed by ice crystals, causing the autopilot to disconnect. The crew reacted incorrectly, leading to an aerodynamic stall from which the jet did not recover.
228: On August 6, 1997, a Boeing 747-3B5, Korean Air Flight 801, crashed on approach to the international airport in the United States territory of Guam, killing 228 of the 254 people aboard. Contributing factors in the crash were fatigue and errors by the flight crew, inadequate flight crew training, and a modification of the airport's altitude warning system that prevented it from detecting aircraft below a minimum safe altitude.
227: On January 8, 1996, an Antonov An-32B aircraft with 6 crew members on board overshot the runway at Kahemba Airport and plowed into a market place. Four on board survived but 225 people on the ground were killed and an estimated 500 were injured (estimated 253 seriously injured). It is the crash with the most non-passenger ground fatalities (not including 9/11). It is usually known as the 1996 Air Africa crash.
225: On May 25, 2002, a Boeing 747-209B, China Airlines Flight 611, bound for Hong Kong International Airport in Hong Kong, disintegrated in mid-air and crashed into the Taiwan Strait 20 minutes after takeoff from Chiang Kai-shek International Airport (now Taiwan Taoyuan International Airport) in Taiwan. It was determined that the crash, which killed all 206 passengers and 19 crewmembers aboard the plane, was caused by improper repairs to the aircraft 22 years earlier when the aircraft encountered a tailstrike.
224: On October 31, 2015, an Airbus A321-231, Metrojet Flight 9268, crashed in the Sinai Peninsula after departing Sharm el-Sheikh International Airport, Egypt, en route to Pulkovo Airport, Saint Petersburg, Russia. All 217 passengers and 7 crewmembers were killed. A branch of the Islamic State of Iraq and the Levant claimed responsibility for bringing down the jet, and a Russian investigation concluded that a bomb was detonated inside the plane at a high altitude.
223: On May 26, 1991, a Boeing 767-3Z9ER, Lauda Air Flight 004, broke up in midair over a remote area of Thailand due to an uncommanded deployment of a thrust reverser on one of the plane's engines, killing all 213 passengers and 10 crewmembers aboard. The flight, which originated at Kai Tak Airport, Hong Kong, and made a stopover at Don Mueang International Airport in Bangkok, Thailand, was en route to Vienna International Airport, Vienna, Austria, when the accident occurred.
217: On October 31, 1999, a Boeing 767-366ER, EgyptAir Flight 990, flying from Los Angeles International Airport, United States, to Cairo International Airport, Egypt, with a stop at John F. Kennedy International Airport, New York City, crashed into the Atlantic Ocean south of Nantucket Island, Massachusetts, killing all 203 passengers and 14 crewmembers. The National Transportation Safety Board determined that the probable cause of the crash was deliberate action by the relief first officer in response to his removal from international service within Egyptair, a finding disputed by Egyptian authorities who maintain another cause of the accident.
213: On January 1, 1978, a Boeing 747-237B, Air India Flight 855, crashed into the Indian Ocean just off the coast of Bombay, India, killing all 190 passengers and 23 crew on board. An investigation concluded that the captain became disoriented after the failure of one of the flight instruments in the cockpit, leading to "irrational control inputs" that caused the plane to crash.
203: On February 16, 1998, an Airbus A300B4-622R, China Airlines Flight 676, en route from Ngurah Rai Airport in Bali, Indonesia, to Chiang Kai-shek International Airport (now Taoyuan International Airport), Taiwan, crashed into a road and residential neighborhood in Taoyuan, Taiwan, killing 182 passengers, 14 crew, and 7 people on the ground. An investigation determined that when the control tower ordered the pilot to abort his landing and "go around" for a second attempt, the pilot, who had unintentionally released the plane's autopilot, did nothing to take control of the plane for 11 seconds as he apparently thought the autopilot would initiate the go around. As the aircraft approached the airport, the pilot executed a sudden steep ascent that produced a stall and crash. China Airlines was also criticized for "insufficient training."
200: On July 10, 1985, a Tupolev Tu-154B-2, Aeroflot Flight 7425, on a domestic Karshi–Ufa–Leningrad route, crashed near Uchkuduk, Uzbek SSR, Soviet Union, on the second leg of its route. All 191 passengers and 9 crew were killed. An investigation concluded that the plane went down due to pilot error. The air crew used an inappropriately low airspeed, causing vibrations which they incorrectly interpreted as engine surges. As a result, they further reduced engine power, causing the aircraft to stall and crash.
In over one hundred years of implementation, aviation safety has improved considerably. In modern times, two major manufacturers still produce heavy passenger aircraft for the civilian market: Boeing in the United States of America, and the European company Airbus. Both place huge emphasis on the use of aviation safety equipment, now a billion-dollar industry in its own right; for each, safety is a major selling point—realizing that a poor safety record in the aviation industry is a threat to corporate survival. Some major safety devices now required in commercial aircraft involve:Evacuation slides – aid rapid passenger exit from an aircraft in an emergency situation
Advanced avionics – computerized auto-recovery and alert systems
Turbine engines – durability and failure containment improvements
Landing gear – that can be lowered even after loss of power and hydraulics
Measured on a passenger-distance calculation, air travel is the safest form of transportation available: Figures mentioned are the ones shared by the air industry when quoting air safety statistics. A typical statement, e.g., by the BBC: "UK airline operations are among the safest anywhere. When compared to all other modes of transport, on a 'fatality per mile basis', air transport is the safest — six times safer than traveling by car; twice as safe as rail."
However, when measured by fatalities per person transported, buses are the safest form of transportation. The number of air travel fatalities per person is surpassed only by bicycles and motorcycles. This statistic is used by the insurance industry when calculating insurance rates for air travel.
Per every billion kilometers traveled, trains have a fatality rate 12 times over air travel; by comparison, fatality rates for automobiles are 62 times greater than air travel. By contrast, for every billion journeys, buses are the safest form of transportation. By the last measure, air transportation is three times more dangerous than car transportation, and almost 30 times more dangerous than bus.
A 2007 study by Popular Mechanics found passengers sitting at the back of a plane are 40% more likely to survive a crash than those sitting in the front. Although this article quotes Boeing, the FAA and a website on aircraft safety, all claim there is no "safest" seat. The article studied 20 crashes, not taking into account the developments in safety after those accidents. However, a flight data recorder is usually mounted in the aircraft's empennage (tail section), where it is more likely to survive a severe crash.
Over 95% of people in U.S. plane crashes, between 1983 and 2000, survived.
In efforts to prevent incidents such as the disappearance of Malaysia Airlines Flight MH370, a new standard has been issued for all commercial aircraft to report their position every 15 minutes to air traffic controllers, despite country of origin. The regulation was scheduled to take effect in 2016 by the ICAO, and requires no new aircraft equipment so long as airlines adhere to it. This requirement is part of a long-term plan, in which by 2020 ICAO will require new aircraft be fitted with data broadcast systems that air traffic controllers are in constant contact with. The plan is called the Global Aeronautical Distress and Safety System.
The Aviation Safety Reporting System (ASRS) collects voluntarily submitted aviation safety incident/situation reports from pilots, controllers and others. The ASRS uses reports to identify system deficiencies, issue alert messages, and produce two publications, CALLBACK, and ASRS Directline. The collected information is made available to the public, and is used by the FAA, NASA and other organizations working in research and flight safety.
The Aircraft Crashes Record Office (ACRO), a non-government organization based in Geneva, compiles statistics on aviation accidents of aircraft capable of carrying more than six passengers, excluding helicopters, balloons, and combat aircraft. Note that ACRO only considers crashes in which the aircraft has suffered such damage that it is removed from service, which will further reduce the statistics for incidents and fatalities compared to some other data.
According to ACRO, recent years have been considerably safer for aviation, with fewer than 170 incidents every year between 2009 and 2015, compared to as many as 226 as recently as 1998.
Annual fatalities have been less than 1,000 in eight of the thirteen years since 2004, with 2013 experiencing the lowest number of fatalities, at 459, since the end of World War II.
2014 included the disappearance of flight MH370 over the Indian Ocean (possible homicide, plane not found apart from minor debris washed ashore) and the shootdown of flight MH17 by pro-Russian separatists in Ukraine as part of the War in Donbass. The total number of fatalities in 2014 was 869 more than in 2013.
Deaths and incidents per year according to ACRO data, as of February 2017:
(Data has significantly changed since November 2015 after a major upgrade to the death rate and crash rate web pages. This may reflect a change between a static and dynamic web page, where data was made to be automatically updated based on the incidents in their archives.)
The European Aviation Safety Agency (EASA) is tasked by Article 15(4) of Regulation (EC) No 216/2008 of the European Parliament and of the Council of February 20, 2008 to provide an annual review of aviation safety.
The Annual Safety Review presents statistics on European and worldwide civil aviation safety. Statistics are grouped according to type of operation, for instance, commercial air transport, and aircraft category, such as aeroplanes, helicopters, gliders, etc. The Agency has access to accident and statistical information collected by the International Civil Aviation Organisation (ICAO). States are required, according to ICAO Annex 13, on Aircraft Accident and Incident Investigation, to report to ICAO information, on accidents and serious incidents to aircraft with a maximum certificated take-off mass (MTOM) over 2250 kg. Therefore, most statistics in this review concern aircraft above this mass. In addition to the ICAO data, a request was made to the EASA Member States to obtain light aircraft accident data. Furthermore, data on the operation of aircraft for commercial air transport was obtained from both ICAO and the NLR Air Transport Safety Institute.
Annex 13 of the Chicago Convention provides the international Standards And Recommended Practices that form the basis for air accident and incident investigations by signatory countries, as well as reporting and preventative measures. The International Civil Aviation Organization (ICAO) is specifically focused on preventing accidents, rather than determining liability.
In Australia, the Australian Transport Safety Bureau is the federal government body responsible for investigating transport-related accidents and incidents, covering air, sea, and rail travel. Formerly an agency of the Department of Infrastructure, Transport, Regional Development and Local Government, in 2010, in the interests of keeping its independence it became a stand-alone agency.
In Brazil, the Aeronautical Accidents Investigation and Prevention Center (CENIPA) was established under the auspices of the Aeronautical Accident Investigation and Prevention Center, a Military Organization of the Brazilian Air Force (FAB). The organization is responsible for the activities of aircraft accident prevention, and investigation of civil and military aviation occurrences. Formed in 1971, and in accordance with international standards, CENIPA represented a new philosophy: investigations are conducted with the sole purpose of promoting the "prevention of aeronautical accidents".
In Canada, the Transportation Safety Board of Canada (TSB), is an independent agency responsible for the advancement of transportation safety through the investigation and reporting of accident and incident occurrences in all prevalent Canadian modes of transportation — marine, air, rail and pipeline.,
In France, the agency responsible for investigation of civilian air crashes is the Bureau d'Enquêtes et d'Analyses pour la Sécurité de l'Aviation Civile (BEA). Its purpose is to establish the circumstances and causes of the accident and to make recommendations for their future avoidance.
In Germany, the agency for investigating air crashes is the Federal Bureau of Aircraft Accidents Investigation (BFU). It is an agency of the Federal Ministry of Transport and Digital Infrastructure. The focus of the BFU is to improve safety by determining the causes of accidents and serious incidents and making safety recommendations to prevent recurrence.
In Hong Kong, the Civil Aviation Department's Flight Standards & Airworthiness Division and Accident Investigation Division are charged with accident investigation involving aircraft within Hong Kong.
Until May 30, 2012, the Directorate General of Civil Aviation investigated incidents involving aircraft. Since then, the Aircraft Accident Investigation Bureau has taken over investigation responsibilities.
Created in 1999 in Italy, the Agenzia Nazionale per la Sicurezza del Volo (ANSV), has two main tasks: conducting technical investigations for civil aviation aircraft accidents and incidents, while issuing safety recommendations as appropriate; and conducting studies and surveys aimed at increasing flight safety. The organization is also responsible for establishing and maintaining the "voluntary reporting system." Although not under the supervision of the Ministry of Infrastructure and Transport, the ANSV is a public authority under the oversight of the Presidency of the Council of Ministers of Italy.
In The Netherlands, the Dutch Safety Board (Onderzoeksraad voor Veiligheid) is responsible for the investigation of incidents and accidents, including air accidents. Its aim is the improvement of safety in The Netherlands. Its main focus is on those situations in which civilians are dependent on the government, companies or organizations for their safety. The Board solely investigates when incidents or accidents occur and aims to draw lessons from the results of these investigations. The Safety Board is objective, impartial and independent in its judgment. The Board will always be critical towards all parties concerned.
In New Zealand, the Transport Accident Investigation Commission (TAIC), is responsible for the investigation of air accidents. "The Commission‟s purpose, as set out in its Act, is to determine the circumstances and causes of aviation, rail and maritime accidents, and incidents, with a view to avoiding similar occurrences in the future, rather than to ascribe blame to any person." The TAIC will investigate in accordance with annex 13 of the ICAO
In Russia, the Interstate Aviation Committee (IAC, MAK according to the original Russian name) is an executive body overseeing the use and management of civil aviation in the Commonwealth of Independent States. This Organization investigates air accidents in the former USSR area under the umbrella of the Air Accident Investigation Commission of the Interstate Aviation Committee.
In Taiwan, the Aviation Safety Council (ASC) is the independent government agency that is responsible for aviation accident investigations. Established in 1998, ASC is under the administration of the Executive Yuan and independent from Civil Aeronautics Administration of Taiwan. The ASC consisted of five to seven board members, including a chairman and a vice chairman, appointed by the Premier. The managing director of ASC manages the day-to-day function of the organization, including accident investigations.
In the United Kingdom, the agency responsible for investigation of civilian air crashes is the Air Accidents Investigation Branch (AAIB) of the Department for Transport. Its purpose is to establish the circumstances and causes of the accident and to make recommendations for their future avoidance.
United States civil aviation incidents are investigated by the National Transportation Safety Board (NTSB). NTSB officials piece together evidence from the crash site to determine likely cause, or causes. The NTSB also investigates overseas incidents involving US-registered aircraft, in collaboration with local investigative authorities, especially when there is significant loss of American lives, or when the involved aircraft is American built.
It is common for an airline to cease using the flight number of a fatal crash, although that is not always the case.