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Suppose a given flight is fully booked and everybody shows up. Not only have they all brought the allowed fully loaded carry-on & checked-in luggage weight but exceed the free-limits. They are all willing to pay extra for, say, an additional 10 Kg per person. Let's assume average weight for all passengers.

  1. Will this cause the flight to go over the Maximum Take-Off Weight? If so, will the flight depart?

  2. What are the measures taken for the passengers & their cargo for such flights? Are they divided to take separate flights?

  3. What if everyone has 20 Kg extra? How about 30 Kg? Is there any limit to it?

  4. Does it add if everyone is overweight?

I am asking this in a general context of a non-budget airline.

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To answer the questions as asked,

  1. We won't depart over the maximum takeoff weight. We'll do something to bring the takeoff weight down to not exceed the limit.
  2. Generally, people fly as scheduled if at all possible, and as much as possible their bags go on the same plane that they do, and other cargo is a lower priority. There are exceptions; passengers might be denied boarding when the plane is simply too heavy with every one and every thing on board, but this is a last resort and not particularly common.
  3. Total weight is total weight, and the more of it there is, the more limited your options become. This is explained in more detail below.
  4. If the people are overweight, it's probably not a factor in the numbers, because for scheduled commercial flights, most airlines use average numbers for passengers and their carry-on bags. So it doesn't matter if they're all skinny or all heavy, they all count for the same "200 lbs". For military charters and sports charters, actual weights are used, and some non-US carriers may use actual weights as well.

Okay, that's the what; let's discuss the "why":

There are a lot of "it depends" elements here, but in most cases, what happens is that the amount of other freight that can be carried gets reduced, and in the worst case some of the bags stay behind. But that's probably fairly uncommon. It's a very worst-case scenario when you can't even take all the passengers -- pretty rare, in my experience.

Your maximum takeoff weight is limited by one of three limits:

  • a takeoff limit (how much the airplane can weigh to take off & climb out while meeting all of the various requirements),
  • an enroute limit (essentially, if you lose an engine at some/any point enroute, can you clear all of the terrain along the way to get to a suitable landing site), and
  • a landing limit (your expected landing weight is no greater than the maximum allowed landing weight).

In practice, the enroute limit is pretty rare, and if the departure runway is long enough, the landing limit is usually the most restrictive. So, most of the time, your limit boils down to: basic weight of the aircraft, plus cargo, plus passengers, plus landing fuel, can't exceed the maximum certified landing weight. The aircraft weighs what it weighs, and a full load of passengers is essentially a given weight (most flights use an "average" weight value rather than actual passenger weights). So the interesting variables are the landing fuel, and the cargo weight (bags plus freight).

If it's a good weather day and no alternate is required, then the required fuel for landing is one number -- let's say 5,000 lbs in a 737, assuming a fairly "best case" sort of day. (Various operators may have slightly different numbers, but this is a high-level explanation, not way down in the details.) But if the weather is bad, that number can go up: allowing fuel for holding, as well as for a possible diversion to an alternate. Depending on how bad the weather is and how far away the alternate, minimum landing fuel might be 8,000-10,000 lbs for a 737, or more.

Thus... my maximum landing weight is 144,000 lbs for a 737-800. If the airplane and the people weigh 125,000 lbs, I have 19,000 lbs left over. If my landing gas is 5,000, then I can take 14,000 lbs of bags/cargo/whatever -- which is a lot. If the weather is crummy at the destination and instead my min landing gas is 12,000 lbs, then I'm limited to 7,000 lbs of bags. If today's flight had 6,000# of bags and 3,000# of cargo, it all goes in the first case, but not in the second, and it's usually easier to let the freight take the next flight than the bags -- it gets expensive to deliver bags that the airline didn't get on the same plane as the passenger!

There can also be instances where the max takeoff weight is more limiting... a high & hot airport and/or short runways can limit how much weight you can take off with. So perhaps "today" where I'm departing, the best that I can do (after considering current winds & temperature and the various runways available) is a max takeoff weight of 165,000#. If I'm burning 25,000# of gas getting where I'm going, then I'll land at 140,000# -- max landing weight (144k) is no longer the limit, max takeoff weight is. And the computation now looks at the various weights plus min TAKEOFF fuel compared to the max takeoff weight, rather than weights plus min landing fuel compared to the max landing weight. But the basic process is essentially the same.

Okay, disclaimer, there are various other things than can come into play that I've glossed over for the sake of simplicity -- max ZFW and improved climb and wet landing runways and plenty of other stuff. If you're studying for your dispatcher license, this is NOT the answer to address all your what-if's. It's just an overview.

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    $\begingroup$ Dispatchers are licensed? $\endgroup$ – Jeffrey Bosboom Jul 17 '16 at 3:53
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    $\begingroup$ @JeffreyBosboom Yep (in the US). There's an FAA exam and everything. $\endgroup$ – Zach Lipton Jul 17 '16 at 4:12
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    $\begingroup$ So if you're unlucky and there's a fat guy convention you didn't know about, could you take off something like 100lb per passenger heavier than the average you're assuming? Would you notice as the passengers filed on that they were all like 280lb plus carry-on and wedging themselves into the seats, prompting you to call the ground crew to take some freight off? Or are the rated weights in any case generous enough that an unusual event like that still doesn't matter? $\endgroup$ – Steve Jessop Jul 17 '16 at 19:24
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    $\begingroup$ @SteveJessop: Not hypothethical, unfortunately : Air Midwest Flight 5481. So really the first claim "We won't depart over the maximum takeoff weight." is not 100% true. It's unlikely that this crash was the only occurrence, statistically many more planes must have taken off overweight. $\endgroup$ – MSalters Jul 17 '16 at 23:30
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    $\begingroup$ I would have thought that the landing gear can report the weight it is supporting, at least approximatly. $\endgroup$ – JDługosz Jul 18 '16 at 7:20
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The situation you described actually happened recently in flights to India from the Middle East. Many bags were simply left behind and carriers were making arrangements to transport them at the earliest. Reasons ranged from avoiding overweight and also the inability to reduce fuel being carried due to monsoons (implying more hover times) in Southern India.

Scores of Indian expatriates in the Gulf who came home for Eid found their baggage left behind due to the massive festival rush.

Executives at some of the Indian carriers said a majority of travellers coming home for the festival had packed heavy bags and were even willing to pay excess baggage charges. But due to load penalty issues — not going beyond the maximum take-off weight of an aircraft without offloading passengers or carrying less fuel — meant that bags had to be left behind

A senior Air India executive said this issue was faced mainly with AI Express flights that operate between Gulf and south India. "Passengers were flying with lots of heavy baggage. Aircraft were carrying more fuel to factor in diversions due to bad weather (heavy rains) or longer than usual hovering times at airports. Due to this bags were left behind and we are making all attempts to ensure that they reach the passengers at the earliest," the executive said.

Source: http://economictimes.indiatimes.com/articleshow/53109304.cms

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The answer so far suggests everybody gets a seat. A customer manager of an passenger airline once told me that's not always the case (I won't mention names here, but this is a famous international airline).

Not everybody who bought a flight ticket will get a boarding pass.

Now, first thing first: no sane pilots will depart with an aircraft that is overweight. An overweight landing might damage the landing gears and require inspection and repair. In the worse case, the capabilities of the aircraft is exceeded (climbing ability / structural limit / flight controls authority etc.) and you crash.

Unless all passengers show up precisely at the same moment, and all travel as a very big group, people are bounded to arrive at the airport, some earlier, some later. Even if they all get to the counters at the same moment, some passengers will check-in first while others wait at the queue. Now, when do we know the weight of the aircraft? After everybody has checked-in? Nope~ with computers, the weight of all checked-in passenger + bags + cargos is known the moment they're checked-in. So the result would be, those who arrive at the airport relatively late will be denied a boarding pass to the flight although there are still empty seats in the cabin.

If anybody has travelled on an "ID pass" (a super-cheap flight ticket sold only to airline's employees and their families), you'd know these passes are always the last to know whether they get a seat. The ground crew have to wait until check-in is closed, then check the standby passenger list, cargo list, standby cargo list (yes there are standby cargos!), only after that will they start considering ID pass travelers. The point here is, cargo carry revenue as well, and while it is easy for the ground crew to deny a cargo box boarding the flight, it's not so easy for the business people to explain why my important package for the international exhibition was delayed 8 hours when my company bought a flight ticket for my package which your airliner promised would get it there.

In the end, it's easier to turn away those who arrived at the airport relatively late. Some airliners overbook flights. That's one reason you can't get on the flight - there are no more empty seats in the cabin. Weight is another reason - there are seats, but no more lifting capability from the aircraft. Always arrive for check-in early!

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    $\begingroup$ Hmmm... I would still think it would be an incredibly extraordinary circumstance for baggage to be chosen over a ticketed passenger when an aircraft is at its weight limit. Honestly, I've never even heard of that happening for any normal-size airliner. I could believe it more on very small regional jets or turboprops, but even then it would be extremely rare. Denied boarding for overbook situations is fairly common, but not so much for weight. $\endgroup$ – reirab Jul 18 '16 at 16:41
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    $\begingroup$ @reirab not baggage to be chosen, but cargo to be chosen. Especially on a large aircraft like 747 or 777. The ground crew almost never tell the px it's weight - it's difficult to explain. It's easier to just tell people they're too late, since under this scheme the ones who don't get a seat are the late ones, so it's fairly easy for people to accept. $\endgroup$ – kevin Jul 18 '16 at 18:30
  • $\begingroup$ A lot of cargo isn't guaranteed, and even if it is, cargo is often cheaper per pound than the IDB penalty (e.g. up to $1350 to lose ~200 lbs). There's actually an IATA cargo priority order for issues just like this, I recall top of the list is human organs for transplant, then AOG equipment, and goes to place perishables like food before general cargo. $\endgroup$ – user71659 Aug 15 '18 at 6:48
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The maximum takeoff weight is an important number. These are the consequences of additional weight on the aircraft.

  1. Slower acceleration on takeoff -> more runway length to reach the same speed.
  2. Slower deceleration if the takeoff needs aborting -> more runway length needed to stop.
  3. Higher stall speed -> aircraft needs more speed on ground to get airborne, at high altitude with thin air the stall speeds become dangerously close to the operating speed.

Flying a commercial aircraft over weight is a never event. The kind of mistake that should never occur. The consequence of doing so is that it turns a minor event that pilots can manage into an incident that the pilots have no safe options.

That said, on one occasion, on a small aircraft in India, the weight was reduced on the aircraft by removing fuel, flying half way to a small airport and then adding more fuel to complete the journey.

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  1. The flight will not depart overweight. In fact, there are a number of factors that can make the max take-off weight variable, including local weather.
  2. Passengers and Bags would probably be kept together where possible, for customer service reasons. It would cost more to reunite bags with passengers than to bump other cargo (freight). One or two extra bags per passenger would not break max take off weight for most commercial airliners. Extra bags on smaller aircraft can definitely be a factor.
  3. Passengers aren't weighed as they board the aircraft. 1 Passenger + Bag generally has a fixed "standard" weight for doing Weight and Balance calculations. Something like 120 kg/Passenger.
  4. The standard weight for Passengers is meant to account for variation. At some point, overweight passengers may be required to buy an additional ticket and use two seats.

In the context of a non-budget airline, it is important to consider that many (Most? All?) non-budget airlines operate freight service with leftover capacity on their flights. Freight gets bumped often due to weight limitations, but generally this is acceptable given the levels of service available in Air Freight. Things that are heavy or bulky cost much more to ship via air at a guaranteed delivery service level. Freight can wait!

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There are at least two possible weight limits on every flight. One is the aircraft's MTOW (Max takeoff weight). Another is determined by the weather, altitude, and runway length: is there enough runway for a safe takeoff? Is there enough obstacle clearance after takeoff, for an aircraft that loses an engine during takeoff?

The weight is estimated by: Empty weight (specific to the aircraft) + cargo + passengers + fuel. Passenger weight is approximated by a formula (although as Americans have gotten fatter, the formula needs tweaking). So the answer to #1 is: "It depends on how far the flight distance is. For short flights, with less fuel, even a very full aircraft is unlikely to violate a weight limit."

No legal pilot will take off with an aircraft that is overloaded. So the answer to #1b is "No, the flight will not depart until something is changed." In the scenario you outlined, they have several choices:

  • Turn away some passengers. Only if they figure out the problem in time, before loading is completed.
  • Offload some luggage at the last minute — as described in previous answer.
  • Reduce fuel load. The only way to do this is to plan on an intermediate stop, which will make everyone late. So this is unlikely.

Good pilots and airlines will try to anticipate problems. On a hot day with a long flight, where the runway length could be a constraint, I expect that they will hold some people on a standby list. Just before departure, they can make all the needed calculations and decide whether to take some or all of the standby passengers. (I don't have personal knowledge of this procedure.)

In San Diego where I live, when the wind changes direction it can decrease the allowed weight, because taking off then requires a different runway. There is a hill near the end of the second runway, which is high enough to reduce the weight limit in some situations!

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    $\begingroup$ "No legal pilot will take off with an aircraft that is overloaded." At least in the GA world, overloaded aircraft are a major contributing cause to crashes. $\endgroup$ – Ron Beyer Jul 17 '16 at 3:54
  • $\begingroup$ @RonBeyer "GA world"? Sorry for my ignorance, but google only suggest Georgia, which I'm sure is not what you intended. $\endgroup$ – Lenne Jul 18 '16 at 6:59
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    $\begingroup$ @Lenne General aviation. Wikipedia sums it up as "all civil aviation operations other than scheduled air services and non-scheduled air transport operations for remuneration or hire" and offer as actual examples of what it is among others "flying clubs, flight training, agricultural aviation, light aircraft manufacturing and maintenance". $\endgroup$ – a CVn Jul 18 '16 at 9:48
  • $\begingroup$ If take-off weight is the concern you could pack on JATO packs until it isn't. $\endgroup$ – Joshua Jul 9 '17 at 14:45
  • $\begingroup$ @Joshua: ...except that civilian aircraft do not generally use RATO. $\endgroup$ – Sean Aug 16 '18 at 0:29
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I think the assumption here is that the airline guarantees the carriage of the bag on the same flight but this is not true. Ref United's policy A.8 in below link

https://www.united.com/ual/en/sg/fly/contract-of-carriage.html#tcm:76-6642

In the event of a foreseeable situation where bags may be more than normal for a flight (eg sports teams, bands), the load-planner may decide to allot more weight/space for the bags. If this is a last minute increase then cargo may be offloaded to release more weight for the bags.

Under certain route conditions, there may not be much cargo and if the aircraft has already been fueled there may not be weight available for the bags, as de-fuelling is a tedious and wasteful procedure it is quite likely that the bags will be left behind.

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I work as a ramp agent for a major airline so I can tell you exactly what will happen in this type of scenario.

Once a checked bag gets weighed, very rarely will we get more than 5 heavy bags for an A320 or A319 type aircraft with 177 passengers max in any one plane and on average we only get 2 heavy bags out of an average of 72 checked bags daily for a full 177 passenger flight.

But! Let's play with your little fantasy of absolute perfect storm of probability here:

If ever! Ever! We get 177 Heavy! bags to load onto an aircraft no one I mean no one! Will load them. These little demon bags we call heavys are responsible for throwing the backs of many ramp agents causing serious spinal injuries that is notoriously common in this occupation.

Honestly the entire occupation reminds me of how reckless humans can be. I work in an airport where people board using an Ada ramp (outdoors boarding) so I see people all the time spitting out their gum on the turmac, littering, smoking near a plane, going under stanchions, ropes, and even jumping over fences to get on the wrong plane as though we create obstacles for them to board! I swear if I get 8 truck tires and lay them down near a plane as to create an obstacle course we will always have 2 to 3 dumbasses a day sprint through it while quickly darting their foot through each tire as though it were a real obstacle course.

So anyway it felt like I threw out my back on that last paragraph so "back" on track here: (pun intended)

The most bags we loaded onto an aircraft at one time was 130 bags with 5 heavys and let me tell you something: God forbid your out of shape when you have to load these bad boys because the pain is coming. Loading each of these bags onto a plane consists of 3 people: one person putting the bag on the conveyor belt, one person receiving the bag on top within the belly of the aircraft (feeding bags) who then slides the bags to the third who is responsible for lifting and stacking the bags neatly against the bulkhead (back wall) however! Sometimes! we are understaffed like at the airport that I work in where there is only one person in the belly receiving the bags and let me tell you my friends, even if you are a cross fit athlete at an Olympic event there is no preparing for this one for it is the ultimate ungodly workout with many having passed out in the bin from an exhaustion. Yes we have had heart attacks while carrying your bags. Vastly underpayed we are dying for your ability to fly so basically like the military we are sacrificing our lives in exchange for your freedom to see your families. God bless us.

So if ever we get 177 bags we will need 5 people to load these whereas on average we only have 2 ramp agents available.

The great news is that they actually have people like me in the world who will load all 177 heavy bags by myself if need be and I can do it all in under 30min. If you don't believe me share this and I will do it as a spectators event.

Realistically a thirdparty carrier will come into assist like fed ex or ups etc.

Hope this helps.

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    $\begingroup$ This doesn't appear to be clearly answering the question and the various issues it raises. At the start it says if you get 177 heavy bags, “no one I mean no one! Will load them.” However, at the end you're suggesting what is required to load them and that you have people like yourself who will do it, which appears to be contradictory. Past that though, what if nobody will load them? What happens logistically? Do some bags get loaded? What happens with the ones that don't? What if you do load them all (since you're also suggesting that might happen), how does the flight manage that? $\endgroup$ – doppelgreener Aug 14 '18 at 15:05
  • $\begingroup$ Great questions sorry I wrote this quickly. The plane has a weight and balance limitation or capacity of how much weight is needed to create lift and if the plane to include fuel, passengers, bags, and basic weight of the aircraft to include commissary items and crew is over that set limitation then weight would be taken off the aircraft with bags being the easiest way to get the job done. $\endgroup$ – John Doe Aug 14 '18 at 15:54
  • $\begingroup$ Randomly selected bags will then get sent to an office where shipping accommodations will be made $\endgroup$ – John Doe Aug 14 '18 at 15:55
  • $\begingroup$ Also if we all refused to load bags it will be treated like a strike for any organization and accommodations like negotiations would be held in getting the rampers to load. It will take Third party companies 3 weeks to get clearance and credentials to load the bags leaving it to management like the stations manager and supervisors to load the heavy bags themselves in which they would most likely do. $\endgroup$ – John Doe Aug 14 '18 at 15:58

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