Fuel Starvation: Why Do Pilots Run Out of Fuel?

Aircraft Fuel. Image: Getty/BanksPhotos

In aviation, like in so many other things, we often scratch our heads over the causes of aircraft accidents. Pilots are human, yes, but things like running out of fuel or flying into the side of a mountain just make you wonder what in the world these particular humans are thinking. Yet these types of accidents are common enough that the NTSB has issued special warnings about them, even distinguishing them as “special emphasis areas” for the purposes of pilot training.

In the pilot training world, this means that flight instructors spend extra time on these topics and every check ride with a FAA designated examiner will certainly include at least a discussion on controlled flight into terrain and fuel management. 

On November 28th, 2016, an Avro RJ85 carrying a Brazilian Soccer team crashed in Colombia, killing 71 people. Speculation arose in the immediate aftermath that the aircraft crashed due to fuel starvation, and the questions piled up. How can two trained airline pilots flying together run out of fuel?

Mechanical problems are rare with all of the redundancy in place, and even in the case of a fuel leak, the pilots should have noticed in time to fly the airplane to a nearby airport. From the last radio transmissions made by the crew, it would seem as if they didn't realize how dire their fuel situation really was. We may never know exactly what happened to LaMia Flight 2933, but it leaves us with the question, why do pilots still run out of fuel?

In flight training, we pay particular attention to these special emphasis areas and we stress to students that running out of fuel happens way too often for anyone to get comfortable with the idea that they’ll never be the one to run out of fuel. We’re always double checking and triple checking fuel, talking about the reasons some pilots run out of fuel, and examining decision making when it comes to fuel management, fuel stops, alternate airports, and fuel reserves.

And then there are checklists. When we preflight the aircraft in flight training, one of the first things a pilot is taught to check is the fuel levels (mostly so that if we need more fuel, we can call the fuel truck early on or plan more time to stop at the self-serve pumps on the way out, but also - clearly - to ensure we have enough to complete the flight.) With two pilots in the airplane, both pilots are taught to check the fuel gauges and then visually check for fuel when possible to ensure that there is, indeed, the appropriate amount of fuel and that the amount somewhat agrees with the fuel gauges. (Fuel gauges in general aviation aircraft are known to be less-then-accurate much of the time.) In addition to these initial checks, there is a preflight checklist that requires the pilot to check the fuel quantity and drain a sample of fuel from the tanks to make sure it’s not contaminated. And during a flight, the cruise checklist and descent checklist often call for the fuel to be monitored or the fuel tank to be switched.

Our flight planning process, when done correctly, should include a close look at fuel planning, including the starting fuel amount, the power setting and coinciding fuel burn for each phase of flight.

And by law, we are required to carry more than enough fuel to make it to our destination, as well as an alternate airport when necessary, plus an addition 30 minutes or 45 minute’s worth of fuel for day and night flights, respectively.  

Finally, in many aircraft, there are, indeed, proper fuel indicators, fuel flow gauges, and even “LOW FUEL” annunciator lights on the panel of most aircraft.  

So why, after all the planning, checklists, system safety, and an emphasis on fuel management, do pilots simply run out of fuel? Well, like all things that seem simple from the outside, it turns out that it’s not that simple.

Fuel starvation in airplanes happens for a variety of reasons, most of which are just plain human error.

1. Improper planning

Improper planning is probably the largest excuse for running out of fuel.

And even after the fact, the pilot rarely acknowledges that his planning was incomplete or just flat-out wrong, because, in their mind, they did everything they knew to do to plan, but "luck" was against them. There are many people who run into bad luck, but there are way more people who just don’t plan well. Or maybe they don’t plan at all. Perhaps they’ve just always had enough fuel and luck on their side to make them confident that fuel won’t just run out, and they’ve gotten lazy about flight planning in general. Or maybe they plan the fuel properly to get to their destination, but don’t plan for an alternate when necessary. 

2. Fuel mismanagement

Fuel mismanagement occurs when the pilot forgets to switch fuel tanks when necessary, or switches to the wrong fuel tank, or just doesn’t monitor the fuel burn during a flight. Much of the time, the problem stems from a lack of understanding of the fuel system itself.

3. Computational error

Rarely a pilot will make a blatant computational error by moving a decimal one place or just interpreting a fuel chart incorrectly If the planned fuel burn is 16.8 gallons per hour, and the pilot plans his flight using 1.68 gallons per hour instead, he will clearly be burning more fuel than planned. Most of the time, the pilot or another crewmember, or even a computer catches the error at some point soon enough to avert disaster, but not always.

4. Poor decision-making

Fuel starvation is often a direct result of poor decision making in multiple areas of the flight. Maybe the pilot didn’t get a proper weather briefing and failed to notice a strong headwind. Or he fails to set the proper power setting and monitor the fuel burn rate. After hours of flying, the weather at the destination deteriorates and night falls, but the pilot decides to try to fly an approach to the airport, anyway, cutting into any fuel reserves that may have been there and leaving no extra fuel for a missed approach or a go around or a subsequent diversion. And even though he may realize that he’s low on fuel, he fails to ask for assistance from ATC and crashes short of the runway. 

5. Not declaring an emergency when a low-fuel situation arises.

Perhaps due to pride alone, pilots are often hesitant to declare an emergency. And when the emergency is due to nothing but poor planning, it’s probably difficult for a pilot to admit to air traffic controllers that he is low on fuel. But there is no good reason not to declare an emergency in a low-fuel situation, especially if other factors are present like bad weather, an inexperienced pilot, or lack of familiarity with the surrounding area. Pilots have been known to run out of fuel trying to figure out where they are after becoming lost or disoriented and refusing to admit it and ask ATC for help.  

6. Guessing or assuming

It sounds like something nobody would ever do when airplanes are involved, but the number of fuel starvation accidents prove that many pilots guess at the amount of fuel in the tanks before taking off, or assume that the last person who flew the airplane filled it up, or assume that because they can see fuel sloshing around in the tank somewhere down there, that there is enough for them to get where they’re going. And some pilots guess at the fuel burn rate, thinking that they can’t be that far off, but over time and distance, or with a strong headwind or a different power setting, they end up being very far off. Guessing or assuming seems like something only other people are dumb enough to do, but it happens more than you think.

7. Distractions

There have been aircraft accidents in the past in which the pilots allowed a fuel starvation event to occur while preoccupied with something else, like fixing a landing gear problem or becoming disoriented. The old adage applies here: Aviate, navigate, communicate — in that order. Troubleshooting or allowing yourself to get distracted by other people or events can lead to fixation on that particular problem or event and can cause the pilot to completely disregard other important aspects of the flight — like fuel management.

8. Failing to plan for deviations from the plan

Pilots who never plan for anything other than their one and only Plan A often find themselves in trouble as soon as Plan A goes awry. Pilots should plan for the worst and hope for the best instead of just planning for the best and counting on it to work out. A pilot who never thinks that anything bad will happen will not have a plan when something bad does happen. Failing to plan for deviations can result in fuel starvation if those deviations require more fuel than originally planned. A pilot's perception is often different from the reality, and assuming that everything will go according to plan is a huge mistake. 

9. Mechanical problem or failure

Very rarely, there is actually a fuel leak or a problem with the fuel system that can cause fuel starvation. In these cases, early recognition is key to recognizing and dealing with the problem. There have been aircraft accidents in the past where the pilots are too preoccupied with other things, or too distracted or just plain lazy, and they aren’t monitoring the actual fuel burn or the status of the fuel system.