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Remembering Tenerife

By Jeff Marcus, Chief, NTSB Safety Recommendations Division

Forty-three years ago, on March 27, 1977, two Boeing 747s, KLM flight 4805 and Pan Am flight 1736, collided on a runway at Los Rodeos Airport in Tenerife, Canary Islands, killing 583 people. It was the single greatest loss of life in aviation accident history.

The crash was the result of an unlikely series of events—and a flight crew’s responses to them.

To begin with, neither of the two aircraft was initially supposed to be at Los Rodeos Airport in the first place. Both planes had been scheduled to arrive at Las Palmas Airport, also in the Canary Islands; however, Las Palmas had just been the target of a terrorist attack, and the terminal had been evacuated and the airport closed. The two 747s, as well as other arriving traffic, were diverted to the smaller Los Rodeos airport in Tenerife, where they landed safely.

The Los Rodeos Airport had not been equipped to handle the influx of diverted flights and, because of that, on March 27, the airport was congested, and maneuverability issues arose when the airplanes were ready to depart. Pan Am 1736 was ready to depart Los Rodeos to resume its itinerary, but had to wait until KLM 4805, which was obstructing the taxiway, had completed taking on fuel from a refueling vehicle. The captain of the KLM flight was instructed to back taxi down the entire runway, then perform a 180-degree turn in preparation for departure. The Pan Am captain was instructed by air traffic control to back taxi down the runway, then exit on the third taxiway to their left, and to report leaving the runway. The taxiways at the airport were unmarked and the centerline lights were out of service.

Los Rodeos airport was subject to fast-appearing, thick fog, and as the KLM airplane lined up for its takeoff roll, fog enveloped the runway. The Pan Am airplane missed its exit, and its crew did not appear to know their position on the runway. Neither crew could see the other plane, and the tower couldn’t see either plane. The airport was not equipped with ground radar.

Having lost so many sources of information, one last source of information failed: verbal communication between the airplanes and the tower.

Immediately after lining up, the KLM captain who had a sense of urgency to depart before exceeding duty limits advanced the throttles and the aircraft started to move forward. The KLM first officer advised the captain that air traffic control (ATC) clearance had not yet been given. The captain replied, “No, I know that. Go ahead, ask.” The first officer radioed the tower that they were ready for takeoff and waiting for ATC clearance. The KLM crew then received instructions that specified the route that the aircraft was to follow after takeoff. The instructions used the word “takeoff,” but didn’t include an explicit statement that the aircraft was cleared for takeoff. The first officer then read the clearance back to the controller, completing the readback with the nonstandard statement: “We are now at takeoff.” The KLM captain interrupted the first officer’s read-back with the comment, “We’re going.”

The controller, who could not see the runway due to the fog, initially responded with the nonstandard terminology “OK,” which reinforced the KLM captain’s misinterpretation that they had been cleared for takeoff. The controller then immediately added “stand by for takeoff, I will call you,” indicating that he had not intended the clearance to be interpreted as a takeoff clearance. However, a simultaneous radio call from the Pan Am crew caused mutual interference on the radio frequency, which was audible in the KLM flight deck as a 3-second-long shrill sound. This caused the KLM crew to miss the crucial latter portion of the tower’s response. The simultaneous message from the Pan Am crew, “We’re still taxiing down the runway, the Clipper 1736!” was also blocked by the interference and inaudible to the KLM crew. Either message, if heard in the KLM flight deck, would have alerted the crew to the situation and given them time to abort the takeoff attempt.

After the KLM plane started its takeoff roll, the tower instructed the Pan Am crew to “report when runway clear.” The Pan Am crew replied, “OK, will report when we’re clear.” On hearing this, the KLM flight engineer expressed his concern about the Pan Am aircraft not being clear of the runway by asking the pilots in his own cockpit, “Is he not clear, that Pan American?” The KLM captain emphatically replied, “Oh, yes,” and continued with the takeoff.

By the time the KLM captain saw the Pan Am airplane, he could only try to fly over it. The tail of the KLM airplane struck the Pan Am airplane, tearing through the center of its fuselage above the wing. Fuel spilled and ignited on impact. Of the Pan Am passengers and crew, 335 died, mainly as a result of ensuing fire and explosions, and 61 survived.

The KLM airplane lost one engine on impact, and the wings were damaged. The airplane rolled sharply and crashed about 500 feet past the point of collision. All 248 passengers and crew died in the crash and the post-crash fire.

The Tenerife accident provided early lessons for the concept of crew resource management (CRM), which emphasizes that all flight crew members should actively voice their safety concerns, and all crew, particularly senior crew members like the captain, must acknowledge the safety concerns of any crew member. In the Tenerife accident, the captain rushed the takeoff, despite the first officer pointing out that they had not received clearance, and the flight engineer recognizing that the Pan Am airplane had not yet cleared the runway. Despite the flight engineer highlighting the dangerous situation, the KLM captain dismissed the concern and continued the takeoff, which resulted in the tragedy a few seconds later.

The Tenerife accident was a milestone in the study of human factors in aviation accidents. The pressures of the day’s events and delays; the logistics pressures in a regional airport handling a major airport’s arrivals; the communications misunderstanding; and the failure to understand and use CRM practices all led to bad decisions at various points in the accident chain.

Aviation has changed and become safer by leaps and bounds since the crash. As a result of Tenerife, there has been greater emphasis on English as the single working language of aviation, and on the use of standard, concise, and unequivocal aeronautical language.

Tenerife was influential in recognizing that all crew members should feel empowered to speak up, and captains should listen to their safety concerns—an important principle of CRM. The principles of CRM have even been extended beyond aviation  to marine safety, where it is known as bridge resource management, and to medicine, where all doctors and technicians in an operating room are encouraged to voice their concerns, and senior, highly esteemed surgeons are trained to listen to and evaluate any safety concern expressed, regardless of who has the concern.

Humans are an integral part of the aviation system and the system must protect for human error. In 2017, many links of an accident chain were in place at San Francisco International Airport when an Air Canada airplane almost landed on a taxiway occupied by four airliners waiting to takeoff. There were over 1,000 people in those four airliners; the accident would have equaled or even surpassed the death toll at Tenerife more than 40 years earlier. That close call was another reminder of how much is on the line every time human pilots and passengers take to the skies—and how much of a role human factors can play in such tragedies and near misses.

Ensuring Transportation Safety, Even During a Crisis

By Member Jennifer L. Homendy

For the past few weeks, I’ve woken up every morning to a text message from the Virginia Railway Express (VRE) updating riders on its continued service and modified schedule. It’s hard not to think of all the VRE and Amtrak locomotive engineers and conductors that I’ve come to recognize (or know by name—Hi, Willie and Samantha!) over the years, and how dedicated they are to continuing to serve the public during this national emergency. You and your colleagues across the country are heroes. Thank you for all you do.

The safety of transportation workers across all modes is extremely important especially during times of crisis. Our nation’s transportation workforce is essential to getting critical goods to states and local communities and to ensuring that those serving on the frontlines of this pandemic, like medical personnel, grocery store employees, and other essential personnel, are able to continue the fight against COVID-19. Without all of them, we’d be in a much more dire situation. Still, we need to make sure that the transportation workers who are putting their lives at risk daily to make deliveries or get people to work are also safe. That not only means providing them with necessary personal protective gear, but also ensuring any regulatory waivers do not jeopardize their safety or the safety of others.

Since the start of this national emergency, many transportation entities facing staffing shortages due to illness and the need to quarantine have requested emergency relief from certain safety regulations. These entities cite concerns about their ability to deliver critical goods and materials necessary for the country’s welfare while meeting regulatory requirements for inspections, training, and maintenance, to name a few. Although regulatory relief from certain requirements may be necessary during this difficult time, I urge the US Department of Transportation (DOT) to carefully review each request and put measures in place to ensure that the safety of transportation workers, and all others who must travel, remains a priority.

We are all being challenged in ways that we could not have imagined a month ago. People are staying safe by traveling only when absolutely necessary and maintaining a safe social distance from others. Those in the transportation industry are also doing what they can to stay safe while continuing to do the important work of moving the people and goods that keep our nation pushing forward during this crisis.

It’s important that any regulatory relief the DOT determines is appropriate is only temporary. This crisis can seem overwhelming, but as a nation, we will prevail. It’s important that when our lives start to take the path back to “normal,” safety regulations—many of which the NTSB has long advocated for following tragic crashes—are reinstituted. Temporary measures to address a crisis should not become the new normal. An efficient transportation network is key to our nation’s success during this challenging time, but we must not forget the importance of ensuring the safety of transportation workers and the traveling public both now and in the future.

A Tribute to NTSB Employees

By Chairman Robert L. Sumwalt

What do you get when you cross a transportation-related life-saving mission with some of the best people in the federal government?

 The National Transportation Safety Board, of course!

 And that is no April Fool’s joke.

 On this day 53 years ago, the NTSB was formed by an act of Congress. The agency’s mission is to investigate every civil aviation accident in the United States and significant accidents in other modes of transportation, determine their probable causes, and issue safety recommendations aimed at preventing future accidents. In addition, we conduct special studies concerning transportation safety, and we coordinate the resources of the federal government and other organizations to provide assistance to victims and their family members impacted by major transportation disasters. We also adjudicate appeals from civil enforcement actions by the Federal Aviation Administration and the United States Coast Guard.


Since 1967, the NTSB has investigated more than 149,000 aviation accidents and thousands of surface transportation accidents. We’ve issued more than 15,000 safety recommendations—the vast majority of which ultimately are implemented. Some of the safety measures that have arisen, at least in part, from our safety recommendations include:


  • Floor-level escape lighting, fire-blocking seat coverings, lavatory smoke detectors, stronger cabin seats
  • Terrain avoidance and warning systems requirements
  • Inert gas use to eliminate fuel tank explosions
  • Shoulder harnesses in general aviation


  • Raising the legal drinking age to 21 and .05 percent BAC drinking and driving laws
  • Child passenger safety
  • Enforcement of commercial vehicle regulations


  • Boating-while-intoxicated laws
  • Cruise ship fire safety
  • Emergency position-indicating radio beacons (EPIRBs) on vessels

Railroad & Rail Transit

  • Positive train control
  • Passenger rail car safety standards
  • Toll-free emergency number posting at grade crossings
  • Tank car enhancements


  • One-call systems before excavation (“Call 811 Before You Dig”)
  • Integrity management programs
  • Facility response plan effectiveness and oversight


  • Hazard communications training for first responders, community planning, and preparedness

I’m often reminded that you can have an important mission, but if you don’t have devoted, talented employees, you really don’t have a great agency. Fortunately, the NTSB has both.

Our mission generates dedication, which often translates to retention; some of our longest-serving employees have been at the agency for over 40 years. But don’t misinterpret that longevity as complacency. In the most recent Federal Employee Viewpoint Survey, of the 70% of NTSB employees who completed the survey, 97% responded favorably to the statement, “When needed I am willing to put in the extra effort to get a job done.” Bear in mind that in many cases, “extra effort” is in addition to routine travel to remote accident sites with only hours’ notice!

During more than 13 years at the agency, including the past 3 as Chairman, I’ve had the pleasure to be surrounded by, and to work with, these professionals. As Chairman, I have relied on them to help formulate strategic decisions, advise me on technical details, and echo and amplify my own thirst for safety improvements.

Many of our air safety investigators are pilots and aircraft mechanics themselves—and each of them can tear down an engine. Several have built their own airplanes. Many of our highway safety investigators come from law enforcement backgrounds. Our marine investigators generally maintain licenses first earned as deck and engine officers or have Coast Guard investigative or regulatory experience. Our railroad and pipeline investigators are veterans of those industries and their regulators as well. Although doctoral degrees are common throughout the agency, the environment is as far as you can imagine from an ivory tower.

The NTSB workforce is among the best in the federal government, which is what fuels my desire to make the NTSB the best place to work in the federal government—even if, for now, we have temporarily moved that workplace into our homes.

Today, like many workforces, we are physically distant from one another, but we are not alone. We are physically separate, but we will get through this together. I’m grateful for the dedication and resilience of every one of NTSB’s employees. And that, too, is no April Fool’s joke.

Attributes of a Healthy Safety Culture

By Chairman Robert L. Sumwalt

I recently wrote a series of social media messages about attributes of a healthy safety culture. I received some interesting feedback and cross-talk from organizational safety leaders, so I wanted to make the collected messages available in PDF form for this blog’s readers.

Attributes of a Healthy Safety Culture

Click on any of the attributes listed below to read the original messages.

I hope that, after viewing these messages, readers look around their operations, note where an attribute is lacking from their organization’s safety culture, and consider whether the shortcoming presents an opportunity for improvement. As widely known expert on organizational accidents James Reason said, “There are no final victories in the struggle for safety.”

While writing these messages, I realized again how integrally enmeshed personal and organizational responsibility are in the safety journey. The active error committed by one employee might not have been committed by another, but the same employee who committed the error might not have done so in another organization. Furthermore, in addition to individuals, an organization might be at the root of an accident.

Continuous safety improvement takes both conscientiousness and boldness to voluntarily identify what might go wrong and to think through the “what ifs” on the way to mitigating risk. It’s a tall order, and my hat is always off to those who accept the challenge—our safety professionals.

I hope that these musings will be of value to you and your colleagues as you move forward in your safety journey!

Automated Vehicles and Distraction: Lessons Learned from Mt. View

By Robert Molloy, PhD, Director, NTSB Office of Highway Safety

The National Transportation Safety Board (NTSB) met on February 25 to consider the 2018 collision of a Tesla Model X, operating with partial driving automation, with a damaged crash attenuator in Mountain View, California. The car steered out of its travel lane and into a gore area, where it collided with the damaged highway safety hardware. The driver didn’t notice the errant path the vehicle had taken because he was interacting with a game application on his work phone.

March 23, 2018, crash of a Tesla in Mountain View, California
Northbound view of the crash scene before the Tesla was engulfed in flames. (Source: witness S. Engleman)

It was a tragic event for both the driver and his loved ones, and the tragedy was compounded because the event was utterly preventable. In this crash, the driver behaved as if his partially automated vehicle were self-driving when it wasn’t. The driver’s resulting distraction, tragically, led to his death. But it’s rare that a crash is the result of a single factor. At the NTSB,  we try to identify all the factors contributing to a crash so we can propose multiple methods to prevent a similar crash in the future. The NTSB doesn’t apportion blame or liability; we look for ways to prevent the next occurrence.

In this crash, we identified or reiterated several ways to prevent a similar tragedy:

  • Because drivers using portable electronic devices while driving often crash, we recommended that device manufacturers find a way to lock people out of their devices while they’re driving.
  • Because “Autopilot,” Tesla’s automated vehicle control suite, is only designed for certain conditions, we reiterated our recommendation to disable it when those conditions are not met.
  • Because Tesla’s proxy measure for driver engagement—torque on the steering wheel—was previously found ineffective, we reiterated a recommendation that Tesla find an effective measure of driver engagement.
  • Because this vehicle crashed into objects that it “did not detect, and [were] not designed to detect,” (a crash attenuator) we recommended that the National Highway Traffic Safety Administration (NHTSA) rate collision avoidance systems under its 5-star rating program, incorporating such objects into its assessment.
  • Because we found that misuse of Tesla’s automation was foreseeable, we recommended that NHTSA evaluate Tesla Autopilot-equipped vehicles to determine if the system’s operating limitations, foreseeability of driver misuse, and ability to operate the vehicle outside the intended operational design domain pose an unreasonable risk to safety, and to ensure that Tesla takes corrective action if safety defects are identified.
  • Because the crash attenuator that the Tesla crashed into had not been repaired, and because lane markings were worn in the area of the crash, we made recommendations to state agencies responsible for maintaining highway infrastructure.
  • Because Apple, the driver’s employer, had no distracted driving policy, we recommended that it adopt one.
  • Because many other companies also don’t have such a policy, and because transportation accidents are a leading cause of workplace injury and death, we recommended that the Occupational Safety and Health Administration review and revise its distracted driving initiatives and add new enforcement strategies.
  • Because it is important to have ready access to data that fits defined parameters to assess crashes involving automated vehicle control, we reiterated recommendations to require standardized data reporting, including incidents, crashes, and vehicle miles traveled, with such systems enabled. This recommendation would also allow the NTSB and NHTSA to evaluate real data on the safety of level 2 automation, not just industry claims.

When we investigate a crash, we aren’t looking for a driver, a company, or an agency to blame; we’re looking for all the ways the next crash can be prevented. When prevention is the goal, those drivers, companies, and agencies are often happy to help make the changes needed to ensure safety. We hope all parties will heed the lessons learned from this tragic crash and take the steps we’ve recommended to increase the safety of the traveling public.


A Comprehensive Approach to Bicycle Safety

By Member Jennifer Homendy

Last fall, the National Transportation Safety Board released a report that made safety recommendations meant to improve safety for an important and growing segment of users on our roadways – bicyclists. The report issued 12 new safety recommendations and reiterated 10 safety recommendations.

Through NTSB’s 50+ years of accident investigation experience, we’ve long known that complex challenges, like reducing the number of vehicle-bicycle collisions, requires multi-faceted solutions. In the study, we looked at numerous countermeasures, including roadway design and infrastructure, reducing traffic speeds, collision avoidance systems and blind spot detection systems.

Homendy-bikePerhaps that is why I was disappointed to see the controversy within the cycling community surrounding one of the 22 recommendations discussed in the report – the singular recommendation about requiring the use of helmets. That debate overshadowed the many other important recommendations that largely focused on preventing collisions between vehicles and bicyclists in the first place, rather than mitigating their severity. As an avid cyclist myself, I am very aware of the hazards that exist for cyclists and share the community’s concern for improving bicycle safety on U.S. roadways.

Separated bike lanes and bike-friendly intersections are incorporated in the design of just a tiny fraction of U.S. roadways. So, we asked for more. The NTSB recommended that guidance provided to highway engineers, city planners and traffic designers, include resources that will help increase bike-friendly roadway improvements throughout the U.S.

Along with changes in infrastructure, the NTSB found that reducing traffic speeds can reduce the likelihood of fatal or serious bicycle injuries. Lowering speed limits is part of a safe systems approach that was also discussed in our 2017 safety study on reducing speeding-related crashes.

Collision avoidance systems are broadly effective in helping motorists detect and avoid other vehicles and some automakers have begun adding systems to detect bicyclists and pedestrians.  To encourage manufacturers to include these systems in their new vehicles, and to assist auto buyers in making safety-conscious purchasing decisions, the NTSB recommended that bicycle detection systems be incorporated into the 5-Star Safety Ratings.

The NTSB also recommended that newly manufactured large trucks be equipped with blind spot detection systems, because large vehicles have bigger blind spots that make it difficult, or even impossible, in some situations for their drivers to see bicyclists.

And as a Board Member, I will continue to push for the implementation of safety recommendations on the NTSB’s Most Wanted List that would help make streets safer for bicyclists – including eliminating distractions, reducing fatigue-related accidents, ending alcohol and other drug impairment, increasing implementation of collision avoidance systems and reducing speed-related crashes.

Member Homendy Bike Safety Study Board Meeting

Implementation of our recommendations would dramatically improve the safety of our roadways for bicyclists. But prevention or avoidance will sometimes fail and mitigating the severity of crashes will help save lives. That basic premise of transportation safety, supported by data on fatalities from head injuries, prompted our call for helmets for bicyclists.

The NTSB’s approach to bicyclist safety is comprehensive, multi-faceted and fact-based. All the safety recommendations, when implemented, would help save lives by preventing collisions from happening, and by reducing the severity of those that do.

2019-2020 Most Wanted List Midpoint Review

By Chairman Robert L. Sumwalt

MWL List

What do you call 125 participants in an NTSB Most Wanted List (MWL) mid-point progress meeting, each of whom has their own idea of a transportation safety goal to achieve by the end of the year?

An excellent start.

On February 4, the NTSB hosted attendees from government, industry, and the advocacy community to discuss progress on the 2019-2020 MWL. The conversations were productive and lively, and there was one thing we all agreed on: we need to achieve more in 2020.

Many people believe the NTSB’s work is done when an investigation has been completed, and we’ve determined the probable cause of an accident. But finding out what happened and why it happened is just half the equation.

The second half is arguably the most important part of our investigations: After determining the what and why, we issue safety recommendations aimed at correcting the deficiencies we uncovered, and thus, preventing similar accidents from happening again.

Even then, our work is still not complete. Recommendations must be implemented by their recipients before they begin to save lives. Therefore, part of our work is to highlight these recommendations and advocate for their implementation.

Board members, safety advocates and other NTSB staff are dedicated to fostering the cooperation necessary to ensure those life-saving recommendations are implemented, so the issues can be addressed and ultimately solved.

The MWL was conceived in 1990 and is the NTSB’s premiere advocacy product. It groups together unimplemented safety recommendations under broad topic areas that we refer to as issue areas. Issues placed on the list are selected from safety recommendations and emerging areas, and are based on the magnitude of risk, potential safety benefits, timeliness, and probability of advocacy efforts to bring about change. Simply put, MWL issue areas are those that we believe need the most attention to prevent accidents, reduce injuries, and save lives.

Up until 2017, the MWL was updated annually. That year, we went to a biennial list, with the provision that we conduct a mid-point progress review. And that, of course, is why we gathered on February 4. The purpose of the meeting was to receive input from stakeholders on where the current list is going, what are the impediments to implementing these recommendations, and what we can do better to advocate successful implementation of these recommendations. It was a day for us at the NTSB to listen to input and feedback.

Prior to the midpoint meeting, only 31 NTSB safety recommendations had been implemented out of 268 targeted in this MWL cycle. Implementing these 31 recommendations will make transportation safer by improving pipeline, aviation, railroad, marine, and highway safety. But as attendees of our mid-point evaluation agreed, implementation of these 31 recommendations, while welcome, is just not enough.

Member Jennifer Homendy and Robert Hall, Director of our Office of Railroad, Pipeline, and Hazardous Materials Investigations, guided the breakout session for that mode. Dana Schulze, Director of NTSB’s Office of Aviation Safety and I facilitated the conversations in the aviation breakout session. The marine safety session was headed-up by Morgan Turrell, Deputy Director of our Office of Marine Safety. And finally, Vice Chairman Bruce Landsberg took the highway safety discussion, joined by Rob Molloy, Director of our Office of Highway Safety.

Here are some of the thoughts that our attendees contributed:

  • Support efforts in the states to strengthen traffic safety laws to address issues like speeding, distracted and impaired driving and seat belt use.
  • Not every solution is a regulatory solution; work with industry and advocates to move toward voluntary compliance to get the required change done.
  • Increase and improve data collection.
  • Be proactive rather than reactive—through increased coordination between the NTSB, agencies, and industry.
  • Identify and promote industry best practices; to make change, it helps to see, hear, and learn from others who have accomplished the task.
  • Increase dialogue between the NTSB and industry outside of the context of accidents through preliminary recommendation communication, site visits, and board member meetings.
  • Creating a safety culture (in business) and addressing negative social norms (in public) are perhaps the most critical steps needed to improve transportation safety overall.
  • NTSB can play a key role in bringing all the key players together, promoting dialogue, and encouraging change.

NTSB recommendations, when implemented, can help to prevent unnecessary deaths, injuries, and property damage. The recommendation that is implemented today could be the life that is saved tomorrow. So, the voices of those closest to the battle for implementation—including the attendees at the midpoint progress meeting—are invaluable.

Time will tell how many critical MWL advances can be achieved by year’s end. I hope it’s all of them.