Another story link:
https://nypost.com/2018/03/13/dog-di...-overhead-bin/
Seems kind of hard to get all of the story details in any single link.
737-900? hm. I was just thinking that UA's 777-300 ER's have a lousy set-up in seats E & F in economy. When the seat supports are consistent for three seats across, and you jam four seats across there, the middle two seats have seat supports in the underseat areas making it difficult if not impossible to store any kind of bag there. Other underseat storage has become difficult with power boxes, etc. But the bad situation has gone worse.

Kind of surprised there was even space in the overhead...

23BC tells me that these passengers were not frequent fliers, and lacking the gut instincts of frequent fliers, and lacking being surrounded by other frequent fliers. UA customer service is deplorable once again. As a Premier Platinum, sometimes I just check-in at the non-premier lines. UA customer service in non-premier areas repeatedly wows me with their impatience and incompetence. Advice to other premiers--try the cattle line occasionally to see how bad customer service gets.