Thin privilege isn’t expecting to get blamed and charged extra when airlines make plane seat widths smaller.

From the article:

The new trend in economy seating reverses a half century of seat growth in economy class. Early jet planes like Boeing’s 707 had 17-inch seats, a dimension based on the width of a U.S. Air Force pilot’s hips, says Airbus marketing chief Chris Emerson. That standard for long-haul flying increased to 18-inches in the 1970s and 1980s with the 747 jumbo and the first Airbus jets. It widened to 18.5 inches with the Boeing 777 in the 1990s and A380 superjumbo in the 2000s. Now, cost-conscious airlines are moving to lighter 17-inch-wide seats on their Boeing 777 and 787 Dreamliners and 18-inch seats for A350s. This doesn’t sit well with many travelers, particularly those who are large or overweight. Arm rests and aisles are also getting slimmed to wedge in the extra seat, meaning more elbows get bumped. And while seats are now being designed more ergonomically, with better cushions and head rests, the improvements don’t stop people from rubbing shoulders.

Or hips, quite obviously.

The average sized US woman is a 14 – that’s a 46" hip. That means 50% of all women in the US have that size or bigger hips. 46" is the circumference, so in order to get the hip width we’ll have to do a little math.

EDIT: For simplicity’s sake I’m making hips a circle instead of an ellipse. This is just a back-of-the-envelope calculation, so please don’t get your knickers in a twist because I didn’t assume a woman’s hips are an ellipse. For an ellipse, the effects are more dramatic – that is, the width required for someone to fit gets larger. So, take the effects produced by the very simple math below and exaggerate them, and there ya go. The point of the post is that the seat sizes are far too small for more people than are being taken into account by your standard “fat person on a plane” news stories.

On to the math:

Remember that the circumference of a circle can be described as 2πr, where r is the radius of the circle and π is the number roughly equal to 3.14. The circumference can also be described as πd, where d is the diameter of the circle.

Hip width is the diameter of the circle. So let’s do a little algebra. Say the circumference is 46 inches. That means:

πd = 46 inches

dividing both sides by π, we get:

d = 14.64 inches

However, when someone sits down their hip circumference tends to spread out a bit due to compression. Taking that into account for a couple inches or so, we have that the average size woman needs about 16.5 inches of space just to fit.

Half an inch isn’t a lot of wiggle room – the average woman can barely fit, and certainly not comfortably, into a 17 inch seat. And when you go up just one size to a size 16 – above which we have almost half of the US population of women – we have a 48 inch hip. Doing the math again, that gives us:

d = 48/π = 15.3 inches

Adding a couple extra inches for compression, we get total needed space of about 17.3 inches. Which is bigger than the 17 allotted inches in refitted planes.

EDIT: Assuming hips are more like an ellipse will exaggerate these effects, making the size needed for the average woman even wider than our simple circular model. It’s likely that a person wearing a size 14 would just fit into 17" airline seats.

67% of US women wear a size 14 or above.

Therefore,

Well over 50% of American women not be able to fit comfortably, or at all, into a 17-inch wide plane seat.

I’d love to see that headline reported somewhere.

-ArteToLife

(source: “The Incredible Shrinking Plane Seat,” Wall Street Journal. Oct 23, 2013)

(some followup comments)