Plane seats are shrinking. In the last 20 years the average seat width has lost a whole 12.7cm, according to advocacy group Flyers Rights. Elbows can't help but overhang today's average plane seat which measures just 76.2cm across.
So, we've got to learn to share.
As airlines move away from jumbos into more fuel-efficient, narrow-body aircraft, more awkward shared-armrest moments will ensue. It's up to passengers to navigate whose arm goes where.
It's not like designers haven't been paying attention. Every year, cabin designers come up with concepts to solve "the armrest war" with ingenious designs such as the paperclip, which features two tiers or slots to separate strangers' forearms.Then, every year, airlines ignore the protests and revolutionary designs - such as the proverbial passenger who feigns a deep sleep immediately after taking your armrest.
It would just be too prohibitively expensive to upgrade the economy armrests across an entire fleet.
As much as I'd like to imagine that "everyone knows the middle seat gets two armrests" there's clearly widespread ignorance or non-compliance. It's the same result, either way.
The idea that passengers can rely on some unwritten "plane etiquette" is a joke. As Aussie comedian Jim Jeffries pointed out, such socially accepted "rules" can be used to behave atrociously.
This is maybe because passengers can't be relied on to follow written rules, let alone unspoken codes of honour.
"Window seat gets armrest and a wall, aisle gets an armrest and leg space, the middle gets both armrests either side." End of.
Flight attendant Boris Millan has written the book on Plane Etiquette, literally.
In 2018, the author of The Common Sense Guide to Flying decided to codify proper plane behaviour in his book: Plane Etiquette in 12 rules. The entire first chapter of which is dedicated to "The Middle Seat."
Although useful for marshalling unruly passengers or settling mid-air disputes, Millan admitted the twelve commandments were "not written in an airplane bible or a part of any air law". They are "simply 'proper etiquettes'".
But could the common armrest tussle all be just some misunderstanding?
The attendant turned author admits noticing that these manners "vary by nationality".
International travel is rife for confusion and good intention lost in translation.
For example Chapter 12 titled "getting off politely" might mean something entirely different to different audiences. UK readers might expect it was a guide to discrete initiation into the mile-high club.
From novel nose-clearing techniques to odd attire, planes host behaviour that would be shocking anywhere else. But while international airspace allows for many different "cultural norms" but personal space is not always one of them.
Instead of being consumed by passive aggressive air rage over a plastic armrest, you could always try talking to your fellow passenger about it.
It couldn't make it any more awkward, could it?
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