The last time my diminutive elderly mother flew to visit me, she had to sit next to a "plus size" woman who was so fat that the armrest between them wouldn't go

The last time my diminutive elderly mother flew to visit me, she had to sit next to a "plus size" woman who was so fat that the armrest between them wouldn't go down, and the woman spilled over into half of my mother's seat. My mom had to spend the 3-hour flight crushed against the opposite arm rest. She tried to get help from the flight attendant, but the plane was completely full so there was nowhere to move either of them. If the solution is for "people of size" to be allowed to take two seats for the price of one, the cost per seat will go up for everyone; this is especially true if, according to the article, 38% of the world is obese and would presumably be able to take advantage of this situation.