blame the "yoga experts"
http://travel.nytimes.com/2013/05/05...anted=all&_r=0
She added that it’s important during long flights to elevate your feet to keep your ankles from swelling. “I’ve gotten off the plane and had those gigantic ankles,” she said. To prevent that, she puts her feet on the bulkhead wall, the back of the seat in front of her or the back edge of the armrest in front of her.