Thursday, August 09, 2007

Bodies as Carry-on Luggage

We're charged for extra luggage, because there are limits to how much weight an airplane can safely carry. But, of course, one of the things that passengers lug onto planes is themselves. An underweight person with extra luggage may well contribute less total burden than an overweight person without. Doesn't it seem strange to charge the less burdensome passenger, in such a case?

It would seem more sensible for airlines to calculate the total per-passenger weight allotment, and charge those who exceed it. (It makes no difference to the airplane whether what's weighing it down is in a suitcase or a suit and tie.) In the present system, we effectively have thin passengers subsidizing the overweight. Is there any good reason for this?


  1. I believe they already charge people who take up more than one seats worth of space for two seats... so perhaps the revolution has already happened.

  2. I would think the airplane's spec's compensate a maximum storage weight with a median passenger weight. That is, by average, a full flight with a full cargo will have an expected weight minus the standard deviation from a maximum human weight. If the mean is 150lbs and the maximum deviation from that is another 150lbs, then the airplane's maximum flight load should be 300lbs per seat plus a set cargo maximum. (Because you don't want an airplane to fly with the difference between lift force and net weight to be zero--because it won't fly!)

    Therefore, only an increase in cargo weight will have an effect on the limitations of the flight; not because of weight, but because of limited cargo space. The same principle applies to passengers only if an overweight person takes up more than one space.

    So, charging extra for heavier cargo is justified, whereas charging extra for a heavier passenger is justified only if the passenger takes up more than one allotted space. American Airlines does this.

    And it is justified here on utilitarian grounds because the chief interest is the engineered safety of the flight.

  3. Jared - if the issue is space, not weight, then why don't they measure and charge for that?

  4. I would have thought the obvious answer is that it is much more difficult to measure space than weight, so weight is used as a proxy measure for space.

  5. Yeah, a 'proxy measure' certainly is the obvious answer. I just found it prima facie implausible because (1) the correlation isn't great, and (2) in most circumstances space is the easiest thing to measure! But perhaps not here.

    Anyway, I'm certainly happy to grant the conditional claim that if space really is the issue, that would justify the status quo.

  6. From the American Airlines webpage:
    "The standard free baggage allowance is the maximum number, size, and weight of bags that each customer is allowed with no additional charge. We have based this allowance on extensive studies of variables that influence the maximum capacity of baggage on an aircraft. These variables include size of aircraft cargo compartments, dimensions of the doors, fuel requirements, typical number of passengers on board, and government regulations. Our evaluation resulted in the establishment of a standard free baggage allowance that is applied to all flights."

    The page further goes on to specify maximum dimensions of luggage for both carry ons and cargo.

  7. i've read elsewhere that airlines regulate baggage weight with a view to protecting their workers from injury via heavy lifting. this too would seem to square with the policies in question.

    that airlines would charge fees for heavy bags with a view to safety seems implausible to me (1) because i have a hard time imagining that passenger luggage could ever be so heavy as to make a plane significantly less safe and (2) because, if heavy bags did pose a considerable risk, it would seem strange to allow them just because their owners had paid a fee. (can you imagine, post-9/11: "well, the extra weight makes this plane significantly more likely to crash, but everyone paid $50, so it's ok.")


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