Originally Posted by
Boltman519
But as a FO checking in early gets you the ability to pick a EC seat for free. I don't know if you can change to it if you have not checked in.
IME you don't have to be checked in to do this. I don't remember why I was changing seats without checking in, but I do remember discovering this.
I'll also add that I received an upgrade about 5 hours prior to departure for a flight a few weeks ago. I was not checked in for the flight. I don't know what would have happened if I was checked in.