Landing on Water: The Power of Human Judgement

A new film this year, “Sully”, tells the story of US Airways Flight 1549 that landed safely onto the water surface of the Hudson River on 15 January 2009 following a drastic damage to the plane’s two engines. This article is specifically about the decision process of the captain Chesley (Sully) Sullenberger with the backing of his co-pilot (first officer) Jeff Skiles; the film helps to highlight some instructive and interesting aspects of human judgement and decision-making in an acute crisis situation. Furthermore, the film shows how those cognitive processes contrast with computer algorithms and simulations and why the ‘human factor’ must not be ignored.

There were altogether 155 people on board of the Airbus A320 aircraft in its flight 1549 from New-York to North Carolina: 150 passengers and five crew members. The story unfolds whilst following Sully in the aftermath of the incident during the investigation of the US National Transportation Safety Board (NTSB) which he was facing together with Skiles. The film (directed by Clint Eastwood, featuring Tom Hanks as Sully and Aaron Ackhart as Skiles, 2016) is based on Sullenberger’s autobiographic book “Highest Duty: My Search for What Really Matters” (2009). Additional resources such as interviews and documentaries were also used in preparation of this article.

  • The film is excellent, recommended for its way of delivering the drama of the story during and after the flight, and for the acting of the leading actors. A caution to those who have not seen the film: the article includes some ‘spoilers’. On the other hand, facts of this flight and the investigation that followed were essentially known before the film.

This article is not explicitly about consumers, although the passengers, as customers, were obviously directly affected by the conduct of the pilots as it saved their lives. The focus, as presented above, is on the decision process of the captain Sullenberger. We may expect that such an extraordinary positive outcome of the flight, rescued from a dangerous circumstance, would have a favourable impact on the image of the airline US Airways that employs such talented flight crew members. But improving corporate image or customer service and relationships were not the relevant considerations during the flight, just saving lives.

Incident Schedule: Less than 2 minutes after take-off (at ~15:27) a flock of birds (Canada geese) clashed into both engines of the aircraft. It is vital to realise that from that moment, the flight lasted less than four minutes! The captain took control of the plane from his co-pilot immediately after impact with the birds, and then had between 30 seconds to one minute to make a decision where to land.  Next, just 151 seconds passed from impact with the birds and until the plane was approaching right above the Hudson river for landing on the water. Finally, impact with water occurred 208 seconds after impact with the birds (at ~15:30).

Using Heuristics: The investigators of NTSB told Sully (Hanks) about flight calculations performed in their computer simulations, and argued that according to the simulation results it had not been inevitable to land on the Hudson river, a highly risky type of crash-land. In response, Sully said that it had been impossible for himself and Skiles to perform all those detailed calculations during the four minutes of the flight after the impact of the birds with the aircraft’s engines; he was relying instead on what he saw with his eyes in front of him — the course of the plane and the terrain below them as the plane was gliding with no engine power.

The visual guidance Sully describes as using to navigate the plane resembles a type of ‘gaze heuristic’ identified by professor Gerd Gigerenzer (1). In the example given by Gigerenzer, a player who tries to catch a ball flying in the air does not have time to calculate the trajectory of the ball, considering its initial position, speed and angle of projection. Moreover, the player should also take into account wind, air resistance and ball spin. The ball would be on the ground by the time the player makes the necessary estimations and computation. An alternative intuitive strategy (heuristic) is to ‘fix gaze on the ball, start running, and adjust one’s speed so that the angle of gaze remains constant’. The situation of the aircraft flight is of course different, more complex and perilous, but a similar logic seems to hold: navigating the plane in air safely towards the terrain surface (land or water) when there is no time for any advanced computation (the pilot’s gaze would have to be fixed on the terrain beneath towards a prospect landing ‘runway’). Winter winds in New-York City on that frozen day have probably made the landing task even more complicated.  But in those few minutes available to Sully, he found this type of ‘gaze’ or eyesight guiding rule the most practical and helpful.

Relying on Senses: Sullenberger made extensive use of his senses (visual, auditory, olfactory) to collect every information he could get from his surrounding environment. To start with, the pilots could see the birds coming in front of them right before some of them were clashing into the engines — this evidence was crucial to identifying instantly the cause of the problem though they still needed some time to assess the extent of damage. In an interview to CBS’s programme 60 Minutes (with Katie Couric, February 2009), Sully says that he saw the smoke coming out from both engines, smelled the burned flesh of the birds, and subsequently heard a hushing noise from the engines (i.e., made by the remaining blades). He could also feel the trembling of the broken engines. This multi-modal sensory information contributed to convincing him that the engines were lost (i.e., unable to produce thrust) in addition to failure to restart them. Sully also utilised all that time information from the various meters or clocks in the cockpit dashboard in front of him (while Skiles was reading to him from the manuals). The captain was thus attentive to multiple visual stimuli (including and beyond using a visual guidance heuristic) in his decision process, from early judgement to action on his decision to land onto the water of the Hudson river.

Computer algorithms can ‘pick-up’ and process all the technical information of the aircraft displayed to the pilots in the cockpit. The algorithms may also apply in the computations additional measurements (e.g., climate conditions) and perhaps data from sensors installed in the aircraft. But the computer algorithms cannot ‘experience’ the flight event like the pilots. Sully could ‘feel the aircraft’, almost simultaneously and rapidly perceive the sensory stimuli he received in the cockpit, within and outside the cabin, and respond to them (e.g., make judgement). Information available to him seconds after impact with the birds gave him indications about the condition of the engines that algorithms as used in the simulations could not receive. That point was made clear in the dispute that emerged between Sully and the investigating committee with regard to the condition of one of the engines. The investigators claimed that early tests and simulations suggested one of the engines was still functioning and could allow the pilots to bring the plane to land in one of the nearby airports (returning to La Guardia or reverting to Teterboro in New-Jersey). Sully (Hanks) disagreed and argued that his indications were clear that the second engine referred to was badly damaged and non-functional — both engines had no thrust. Sully was proven right — the committee eventually updated that missing parts of the disputed engine were found and showed that the engine was indeed non-functional, disproving the early tests.

Timing and the Human Factor: The captain Sullenberger had furthermore a strong argument with the investigating committee of NTSB about their simulations in attempt to re-construct or replicate the sequence of events during the flight. The committee argued that pilots in a flight simulator ‘virtually’ made a successful landing in both La Guardia and Teterboro airports when the simulator computer was given the data of the flight. Sully (Hanks) found a problem with those live but virtual simulations. The flight simulation was flawed because it made the assumption the pilots could immediately know where it was possible to land, and they were instructed to do so. Sully and Skiles indeed knew immediately the cause of damage but still needed time to assess the extent of damage before Sully could decide how to react. Therefore, they could not actually turn the plane towards one of those airports right after bird impact as the simulating pilots did. The committee ignored the human factor, as argued by Sully, that had required him up to one minute to realise the extent of damage and his decision options.

The conversation of Sully with air controllers demonstrates his assessments step-by-step in real-time that he could not make it to La Guardia or alternatively to Teterboro — both were effectively considered — before concluding that the aircraft may find itself in the water of the Hudson. Then the captain directed the plane straight above the river in approach to crash-landing. One may also note how brief were his response statements to the air controller.  Sully was confident that landing on the Hudson was “the only viable alternative”. He told so in his interview to CBS. In the film, Sully (Hanks) told Skiles (Ackhart) during a recuperating break outside the committee hall that he had no question left in his mind that they have done the right thing.

Given the strong resistance of Sully, the committee ordered additional flight simulations where the pilots were “held” waiting for 35 seconds to account for the time needed to assess the damage before attempting to land anywhere. Following this minimum delay the simulating pilots failed to land safely neither at La Guardia nor at Teterboro. It was evident that those missing seconds were critical to arriving in time to land in those airports. Worse than that, the committee had to admit (as shown in the film) that the pilots made multiple attempts (17) in their simulations before ‘landing’ successfully in those airports. The human factor of evaluation before making a sound decision in this kind of emergency situation must not be ignored.

Delving a little deeper into the event helps to realise how difficult the situation was.  The pilots were trying to execute a three-part checklist of instructions. They were not told, however, that those instructions were made to match a situation of loss of both engines at a much higher altitude than they were at just after completing take-off. The NTSB’s report (AAR-10-03) finds that the dual engine failure at a low altitude was critical — it allowed the pilots too little time to fulfill the existing three-part checklist. In an interview to Newsweek in 2015, Sullenberger said on that challenge: “We were given a three-page checklist to go through, and we only made it through the first page, so I had to intuitively know what to do.”  The NTSB committee further accepts in its report that landing at La Guardia could succeed only if started right after the bird strike, but as explained earlier, that was unrealistic; importantly, they note the realisation made by Sullenberger that an attempt to land at La Guardia “would have been an irrevocable choice, eliminating all other options”.

The NTSB also commends Sullenberger in its report for operating the Auxiliary Power Unit (APU). The captain asked Skiles to try operating the APU after their failed attempt to restart the engines. Sully decided to take this action before they could reach the article on the APU in the checklist. The operation of the APU was most beneficial according to NTSB to allow electricity on board.

Notwithstanding the judgement and decision-making capabilities of Sully, his decision to land on waters of the Hudson river could have ended-up miserably without his experience and skills as a pilot to execute it rightly. He has had 30 years of experience as a commercial pilot in civil aviation since 1980 (with US Airways and its predecessors), and before that had served in the US Air Force in the 1970s as a pilot of military jets (Phantom F-4). The danger in landing on water is that the plane would swindle and not reach in parallel to the water surface, thus one of the wings might hit water, break-up and cause the whole plane to capsize and break-up into the water (as happened in a flight in 1996). That Sully succeeded to safely “ditch” on water surface is not obvious.

The performance of Sullenberger from decision-making to execution seems extraordinary. His judgement and decision capacity in these flight conditions may be exceptional; it is unclear if other pilots could perform as well as he has done. Human judgement is not infallible; it may be subject to biases and errors and succumb to information overload. It is not too difficult to think of examples of people making bad judgements and decisions (e.g., in finance, health etc.). Yet Sully has demonstrated that high capacity of human judgement and sound decision-making exists, and we can be optimistic about that.

It is hard, and not straightforward, to extend conclusions from flying airplanes to other areas of activity. In one aspect, however, there can be some helpful lessons to learn from this episode in thinking more deeply and critically about the replacement of human judgement and decision-making with computer algorithms, machine learning and robotics. Such algorithms work best in familiar and repeated events or situations. But in new and less familiar situations and in less ordinary and more dynamic conditions humans are able to perform more promptly and appropriately. Computer algorithms can often be very helpful but they are not always and necessarily superior to human thinking.

This kind of discussion is needed, for example, in respect to self-driving cars. It is a very active field in industry these days, connecting automakers with technology companies for installing autonomous computer driving systems in cars. Google is planning on creating ‘driverless’ cars without a steering wheel or pedals; their logic is that humans should not be involved anymore in driving: “Requiring a licensed driver be able to take over from the computer actually increases the likelihood of an accident because people aren’t that reliable” (2). This claim is excessive and questionable. We have to carefully distinguish between computer aid to humans and replacing human judgement and decision-making with computer algorithms.

Chesley (Sully) Sullenberger has allowed himself as the flight captain to be guided by his experience, intuition and common sense to land the plane safely and save the lives of all passengers and crew on board. He was wholly focused on “solving this problem” as he told CBS, the task of landing the plane without casualties. He recruited his best personal resources and skills to this task, and in his success he might give everyone hope and strength in belief in human capacity.

Ron Ventura, Ph.D. (Marketing)


(1) “Gut Feelings: The Intelligence of the Unconscious”, Gerd Gigerenzer, 2007, Allen Lane (Pinguin Books).

(2) “Some Assembly Required”, Erin Griffith, Fortune (Europe Edition), 1 July 2016.


One thought on “Landing on Water: The Power of Human Judgement

  1. Danny Rainer

    As someone who followed-up on this incident very closely and also watched the excellent movie, I congratulate Dr. Ron Ventura on yet another insightful article!

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