Originally Posted by my2cents
...This last, and most detailed, answer was that the plane is now a 3-class cabin and the 4th row is now considered Business Class. Apparently when it was a 2-class cabin there were some people who were really supposed to be in BC but were put in FC for that leg of their itinerary. Now that it's 3-classes their seats are considered FC and they need to be moved to BC seats. We OTOH were assigned seats that are now in BC but I was told we can't move into FC seats until those BC people have been officially downgraded and the seats are freed up.
The part about the equipment swap makes sense... except for a couple of things: I hope they told you the 4th row and not row 4, as no UA 3-class have row 4 in BC; also you say both that your seats are N/A, and that you have seats assigned in BC.
It is not unusual (I guess that makes it "normal") to have and a/c swap on a flight, and this in turn kicks off a game of musical chairs.
OTOH, FC (and even BC) on an international plane is better than on a domestic one, so you're better off.