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The FAA states

To keep you and your family as safe as possible during flight, FAA regulations require passengers to be seated with their seat belts fastened:

  • When the airplane leaves the gate and as it climbs after take-off.

  • During landing and taxi.

  • Whenever the seat belt sign is illuminated during flight.

Why is it important to follow these safety regulations? Consider this:

  • In nonfatal accidents, in-flight turbulence is the leading cause of injuries to airline passengers and flight attendants.

  • Each year, approximately 58 people in the United States are injured by turbulence > while not wearing their seat belts.

  • From 1980 through 2008, U.S. air carriers had 234 turbulence accidents*, resulting in 298 serious injuries and three fatalities.

  • Of the 298 serious injuries, 184 involved flight attendants and 114 involved passengers.

  • At least two of the three fatalities involved passengers who were not wearing their seat belts while the seat belt sign was illuminated.

  • Generally, two-thirds of turbulence-related accidents occur at or above 30,000 feet.

It is quite possible that the FAA is correct to say that wearing a seatbelt while flying reduces the risk of death and injury.

My question is: If this be true, what precisely (quantitatively, statistically) is the magnitude of this safety benefit? This includes ALL possible sources of risk of injury or death, including turbulence, crashes, and anything else conceivable (e.g. slightly reduced risk of someone drunk pulling you out of your seat and throwing you out of the plane).

A possible statistic might be something like: Number of deaths avoided, per 1 million hours with seatbelt fastened, when seatbelt light is on (as compared to not fastening the seatbelt when the light is on).

How in turn does this compare to other safety measures that most people do not take, but ought to (at least according to some experts)? For example, wearing a mask to reduce the risk of death from flu. If, while in public, I wear a mask for 1 million hours, presumably my risk of death from flu decreases a little. How does this compare to the benefit from my fastening my airplane seatbelt for 1 million hours?

Or, as another example, wearing a helmet while cycling to reduce the risk of death from a cycling accident, which, again, is a recommendation by some.

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    Another possible benefit in the case of a crash (whether catastrophic or not) is that it might help identify victims. Victims who are still strapped into their assigned seats would be easier to identify ("the corpse in seat B5? Oh, that's John Smith's seat, so it's probably him"). – Rob Watts Oct 17 '14 at 17:04
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    All I have is an anecdote which I know is worthless here, but one time I was flying the turbulence/drops were so extreme that I was certain anyone without a seatbelt would've hit the ceiling. Maybe not true, it's been a decade, but it was truly some extreme turbulence -- worst I'd experienced in like 40+ national and intl flights. – HC_ Oct 17 '14 at 19:24
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    You've edited the question to imply that the decision should made by/justified by the individual's personal risk. I think that moves away from a notable claim. The law-makers and/or airlines who set these rules presumably consider bigger picture issues: one person's risk of whiplash and broken bones may be worthwhile to them, but what do they do if 200 people get injured at the same time in the air? How will their insurance premiums change? How will these stories affect sales to a fickle public? Personal liberties to adopt risk may not be high on their priority list. – Oddthinking Oct 19 '14 at 1:56
  • If it considerably reduces your risk of injiury in case of turbulence (and I think this sounds totally plausible), the the question whether it saves you from death in case of X does seem totally irrelevant to me. It might be an interesting statistical study, but what would we learn from it? – Martin Oct 19 '14 at 20:29
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    @Oddthinking: There's also the issue that an unsecured human body can be a risk to other passengers. – Flimzy Oct 19 '14 at 23:25
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Unlike seatbelts found in cars, a seatbelt on an airplane isn't there to save you if the plane slams front first into the ground or is hit by a missile.

It's there to keep you safe in the event the plane makes a sudden move or has a minor accident. This commonly happens when flying through turbulence. Sudden movements could also happen during a bad takeoff or landing. If you aren't strapped in and the plane drops a hundred feet then you will be in a short free fall that would separate you from your chair. Once things were back under control you might land back in your chair, or you could land on top of a fellow passenger or elsewhere.

Why you should keep your seat belt on in a plane

Apparently This Matters: Airplane seat belts

The following link is to a story about a plane that hit turbulence and dropped all of 60+ feet:

Chaos on Singapore airlines flight

The FAA states that 58 people in the US per year (link) are injured due to not wearing their safety belt when a plane experiences turbulence.

From 1980 through 2008, there were 234 turbulence "accidents" in which 298 people sustained serious injury and 3 died. At least 2 of those deaths were due to failure to wear the seat belt. With a bit more research you might be able to locate the number of miles flown in the US during that time period, but I suspect it's a rather large number.

This Federal Aviation Authority Fact Sheet contains a breakdown of crew and passenger injuries caused by turbulence from 2002 through 2013.

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    I believe the main reason you keep your seat-belt on by default is the very rare but dangerous occurrence of completely unexpected turbulence. You can be flying smooth and then, out of nowhere, the plane drops 100 feet in a few seconds. (I think this is it: en.wikipedia.org/wiki/Clear-air_turbulence) – MGOwen Oct 18 '14 at 2:58
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    @Emrakul I don't see how you come to that conclusion. Wearing a seatbelt in flight mitigates the tiny risk of dying because of turbulence, the small risk of being seriously injured because of turbulence and the larger risk of being slightly injured because of turbulence. Unless there are confounding factors, it looks like a clear (but small) win. – David Richerby Oct 18 '14 at 9:45
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    @Emrakul In addition, in contrast to Kenny LJ (OP)'s example of wearing full body armor in a small town, wearing a seatbelt in a plane is not very inconvenient and takes only a little bit of extra effort on the passenger's part. – Kevin Oct 18 '14 at 20:13
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    @Emrakul: If 99% follow the "fasten seat belt sign", 1 dies with and 2 die without seatbelt, then we can expect 200 would have died if nobody wore their seatbelt. – gnasher729 Oct 19 '14 at 15:59
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    Alright, guys, I get the point. Enough already. Four notifications telling me I'm wrong is plenty. One sufficed. Thanks. I get it, really. – Aza Oct 19 '14 at 17:24

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