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How dangerous can it be if something falls from a flying aircraft?

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    $\begingroup$ "A thorough preflight is performed in order to ensure that all parts will remain flying in close formation for the duration of the planned flight." (I forget who said that first, but I've long since stolen it.) $\endgroup$
    – voretaq7
    Oct 3, 2014 at 17:07
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    $\begingroup$ If you consider bombs as well, very dangerous. $\endgroup$
    – kevin
    Nov 2, 2014 at 8:09
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    $\begingroup$ @HCBPshenanigans You absolutely cannot neglect air resistance. It's highly significant and terminal velocity of almost any object is much, much less than the freefall speed would be from 10km in a vacuum. (The latter would be about 450m/s, i.e., 1000mph.) $\endgroup$
    – David Richerby
    Nov 2, 2014 at 11:17
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    $\begingroup$ Oh, and air resistance is definitely not something you can ignore... ever... once you get out of high school sophomore physics class. Especially when dealing with something like a paper E6B computer. I have to imagine that its terminal velocity is pretty small. $\endgroup$
    – Keegan
    Nov 4, 2014 at 4:32
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    $\begingroup$ How dangerous? Very. $\endgroup$
    – Mark
    Jul 3, 2015 at 1:23

7 Answers 7

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The standard operating procedures state that before every flight, a thorough pre-flight inspection should be performed. Depending on the aircraft, minute and tiny details are not even omitted.

Things do not normally and occasionally fall off from a flying airplane, the same way as different objects do not fall from a driving car, although the pre-drive inspection of a car is no where nearly as comprehensive as the pre-flight inspection. Yet, how many times we have seen a bumper, guard, muffler or rear-view mirrors falling off?

How dangerous it would be when it happens? This depends on the part which has fallen. Some parts are not noticeable until landing or next inspection and some can cause disasters.

Baltimore Sun reports this:

No deaths or injuries have been reported in such incidents, but the Federal Aviation Administration is not even 100 percent certain of that.

The proper term for this incident is Things Falling Off Aircraft (TFOA). The pilot must then submit a hazardous material report within 24 hours in case the material can cause further harm.

This site has listed some TFOA incidents:

  • In August 2000, a KLM Royal Dutch Airlines Boeing 747 was forced to make an emergency landing when some engine pieces plummeted to the ground and landed on a crowded Los Angeles beach
  • On March 10, 2005, a couple taking a stroll through woodlands near Gatwick airport had a lucky escape when a door from a passing British Airways jet, crashed to earth. A part of the 70-pound door from a Boeing 777 had become dislodged just after take off and missed the couple by only 20 feet!
  • On August 11, 2006, a door fell off from a TAM Fokker 100 from Sao Paulo to Rio de Janeiro. It dropped off 18 minutes after departure but the plane was able to return to Sao Paulo without incident. Nobody was injured.
  • An engine exploded on a Japan Airlines flight bound for Tokyo with pieces of the engine falling on a neighborhood in Jakarta. The falling debris hurt no one but 16 homes were damaged.
  • The right wheel of a Blue Panorama Airlines Boeing 737 fell off after it departed from an airport in Spain and was forced to make an unscheduled landing amid emergency in Rome.
  • A similar incident happened near Los Angeles where an American Airlines Boeing 757 lost its right nose gear but managed to land safely with 105 passengers on board.
  • A landing gear door fell off a Delta Airlines Boeing 727 shortly after the plane took off from Boston*s Logan International Airport. The 30-pound metal door crashed into an empty street in a quiet residential neighborhood.
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    $\begingroup$ @Farhan "The right wheel of a Blue Panorama Airlines Boeing 737 fell off after it departed from an airport in Spain and was forced to make an unscheduled landing amid emergency in Rome." The wheel was forced to make an emergency landing in Spain? $\endgroup$
    – Bassinator
    Oct 29, 2014 at 19:25
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Answer - Very dangerous!

I have 1st and 2nd hand information, so I can speak reliably on this issue. In 2005, a NW DC-10 from MSP to HNL noticed abnormal heat (TIT) on #2 Engine on their final approach. The Operations Dept., where I worked at the time, told them that the thrust reverser for #2 had fallen off on the initial climb (approximately 8,000 ft.), and landed in a field adjacent to a public golf course, next to where a lead mechanic lived and he reported it to OP's, as the plane was making their final approach in HNL.

Independently, my 2 sisters were playing a round of golf at that golf course at the time, when one of them looked up in the air, pointing at a large object rapidly falling and said, "What's that?" Later, the following day, I got a good look at 6-7' round, composite metal object weighing about 300-400lbs with a lot of grass embedded into it (how does grass get embedded in the #2 thrust reverser-the engine mounted right below the rudder?) sitting on a pallet on the hangar floor. Needless to say, an object that size and weight falling from that height could REALLY do some serious damage.

But why did it happen?

DC-10's are mostly retired from service now, giving way to much more fuel-efficient airplanes, but it was not common practice to use the #2 thrust reverser, so when 'A' or 'B' checks came around, it was commonly not looked at, as there was 'theoretically' no reason to do so. The card did come up on "C" checks, but the now-deceased NWA had a policy of 'farming out' "C" checks overseas, in which case it was someone in MSP 'verifying' work was done in Honduras, Singapore, China, and elsewhere. Ignore something long enough, especially on a heavy commercial aircraft with lots of vibration and you will reap the consequences! The company immediately inspected all other DC-10's in it's fleet and found several others approaching the shear point that the original one did.

The crew was unaware it had detached in flight; it presented no compromise in the airworthiness(in a normal situation), and it wasn't until it's final approach some 8 1/2 hrs later that they noticed something peculiar, which was verified by OP's. But it could have been a catastrophe on the ground, and it speaks to the fact that there are no shortcuts to safety, no matter how cheap the ticket prices are.

Further information can be found here.

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    $\begingroup$ I'm assuming it was verified that the embedded grass wasn't a result of smashing into a golf course lawn at high velocity? $\endgroup$
    – reirab
    Jul 3, 2015 at 2:17
  • $\begingroup$ @reirab Couldn't say for sure, maybe some Chinese mechanic pounded in copious amounts of Burmuda grass before he re-attached the thrust reverser-you probably couldn't tell the difference....;>) $\endgroup$
    – user2479
    Jul 3, 2015 at 4:35
  • $\begingroup$ I thought the tail-mounted DC-10 engine was #2. #3 would be the right wing engine, would it not? $\endgroup$
    – Fred Larson
    Jun 20, 2017 at 19:52
  • $\begingroup$ @FredLarson Absolutely Right-My Bad! The #2 Engine sits directly under the rudder on the tail. Same configuration for the 727-I should know better. Thanks. $\endgroup$
    – user2479
    Jun 21, 2017 at 23:01
  • $\begingroup$ @user2479: Not quite the same configuration - on a 727, all three engines are on the tail (the #2 in the middle, pointing straight out the ass end of the plane, with an S-duct; the #1 and #3 on the sides of the empennage). With the DC-10, the #1 and #3 engines are on the wings - only the #2 engine is on the tail. $\endgroup$
    – Vikki
    May 25, 2018 at 15:32
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A Boeing 757's just been in the news, flight TCX1638 from London Gatwick to Hurghada Egypt.

Shortly after takeoff its emergency escape slide, as well as the unit it was housed in, fell off the jet!

The above photo is of the 4 meter / 13 feet long chute housing that detached. Luckily it landed in a field; I can only imagine the potential for damage it could've had!

Kent Police stated:

The aircraft part that police have been looking for is said to be an overwing emergency slide unit (similar to the one pictured) that is believed to house one of the evacuation chutes that deploy in an emergency after a plane has landed. The uninflated chute is believed to have been trailing from the unit as it fell to the ground.

The AAIB has launched an investigation.

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Probably not, but it is possible that due to structural failure an engine, vertical stabilizer or the entire plane itself will fall down. Though often the plane will come down shortly after.

It is possible that a small leak lets the waste of the toilet seep out and freeze to the fuselage which can let go and come down in a big chunk.

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    $\begingroup$ The Boeing 727 could be damaged itself by that toilet ice breaking loose; it could then be sucked into the port engine. This did happen at least three times $\endgroup$
    – Peter Kämpf
    Oct 3, 2014 at 16:33
  • $\begingroup$ @PeterKämpf: Why specifically the #1 engine, and not ol' #3? $\endgroup$
    – Vikki
    Mar 23, 2019 at 21:33
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    $\begingroup$ @Sean: The toilet water outlet was ahead of the intake on that side. When ice accumulated there and then suddenly broke off, it could knock a few blades from the engine compressor. The resulting imbalance would overload the engine mounts. $\endgroup$
    – Peter Kämpf
    Mar 24, 2019 at 22:19
  • $\begingroup$ @PeterKämpf: So why didn't they put the toilet drain somewhere other than right in front of an engine intake? $\endgroup$
    – Vikki
    Mar 25, 2019 at 2:40
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    $\begingroup$ @Sean: Good question. Seems nobody is infallible. $\endgroup$
    – Peter Kämpf
    Mar 25, 2019 at 9:13
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One major issue that must be kept in mind is the sheer lack of probability that something falling from the sky would ever hit somebody. As a relatable example, it is estimated that over 500 meteorites actually strike the surface of the earth every year, the vast majority of which never hit anyone or anything of value. The reason is that there is a looooooot of unused space on this planet of ours, space between continents, major cities, even houses inside of said city. (Also keep in mind that even if a large object hits a house, no matter the origin, that doesn't mean that anyone in the house will be hurt. Living quarters also have a lot of empty space in them.)

I mean, keep in mind, there have been a lot of cases of entire planes falling out of the sky and for the most part nobody is hurt except (sadly, though inevitably) the people on the plane. This can even be true when it's near a populated center. Because there is a lot of empty space even near big cities.

So, yes, I would agree with the other answers that being hit in the head with a piece of junk from an aircraft would be dangerous, probably deadly. But I would contest that the chances of it actually happening are extraordinarily small. Not impossibly, but very very small.

Thus, to actually answer your question: I'd say that the vast majority of the time an object falling off of a plane isn't dangerous at all.

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    $\begingroup$ Except that, when entire planes fall out of the sky, it's most often close to take-off or landing, which means the plane is near an airport, which means it's over or near a populated area. So quite often people are killed on the ground. $\endgroup$
    – David Richerby
    Nov 2, 2014 at 11:22
  • $\begingroup$ @DavidRicherby I'd love to see some stats on that if you have them. I tend to read crash reports quite often out of curiosity (even going to the NTSBs database to just check around.) My gut tells me that the majority of aircraft incidents do not involve ground fatalities. They do occur, don't get me wrong, but in the vast majority of aircraft accidents, nobody on the ground is hurt. $\endgroup$
    – Jae Carr
    Dec 17, 2014 at 19:19
  • $\begingroup$ I only said "quite often". My impression is also that the majority of incidents don't cause fatalities on the ground. Off the top of my head, the Air France Concorde crash and El Al 1862 both killed people on the ground, near airports. $\endgroup$
    – David Richerby
    Dec 17, 2014 at 19:29
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    $\begingroup$ @DavidRicherby Oh, my apologies, I was in "LSAT Mode" where quite often would be interpreted as "A bit over 50% of the time" as opposed to the more colloquial sense of "it happens more than you might think." Apologies, I just misunderstood :). $\endgroup$
    – Jae Carr
    Dec 17, 2014 at 19:39
  • $\begingroup$ It's true that most plane crashes don't involve victims in the ground, but they involve victims on the ground often enough to be a concern. The same reasoning could be applied to mosquito bites: an overwhelming proportion of mosquito bites don't carry malaria, but the tiny proportion that carry malaria amounts for hundreds of thousands or millions. $\endgroup$
    – Pere
    Dec 28, 2016 at 15:36
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Sample of two engine uncontained failures:

In both cases, large chunks of rotor discs "went missing". Had they hit someone, it would surely be fatal. Extensive searches were conducted, because they were important in the forensic analysis.

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Back in propellor days, airliners would vent waste water from the lavatories on occasion. When jet aircraft began flying at very high (and very cold) altitudes, this could lead to the waste water freezing, and large chunks of ice falling at high speed, so the practice was discontinued.

Many years ago, I recall seeing a photo of a poo-sickle from an airliner that came through the roof of someone's house.

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