Originally Posted by
canadiancow
I've seen that happen to others.
They're pretty strict about it. I assume they have to do an override if there are other seats available or it's not at the gate, and that probably requires justification.
Yup, and it's also creating the situation I frequently see on UA on not-full flights. The back of Y is completely full but lots of empty middle seats (or even rows) in the preferred section.