Originally Posted by
Kacee
Unfortunately, it transitions to whatever seat UA puts you in. There is no automatic mapping. Sometimes they will respect your initial selection, others it will a random reassignment. Good idea to watch these reservations pretty closely so you can get on it quickly if they swap and give you a crappy seat.
Not specific experience on these planes, but in the past I've found that if the same number seat exists on the "new" plane (one swapped in) you often end up in it, but if it doesn't then you're stuck in something random.
Of course, on this plane that's feast or famine - Row 16 (bulkhead) turns into some middle seat. (and that's what happened to me before the rows were consistently numbered - I went from 6C (bulkhead, I think that's number) to 28E or something when the newer airbus started in row 7.