I had never seen one of these before today. They’re great. Way better than reaching for a single pole in a crowded car and wrapping your hand around some stranger’s fingers. And If you have the whole thing to yourself you can hook your arm through it.
OP said Seattle, but I’ve also seen them at Denver
I just saw that the OP said Seattle airport and that’s plausible for me. I’m going to choose to think that was it and save myself the mental agony.