Why is there no seat choice available on the A319?
Looking to book an upcoming flight with a connection from ZRH to VIE, I have the option of a 1h10m or 3 hour connection.
The shorted connection is an A319 and the longer one is an A321. if I pick the A319 there are no seat options at all (only window or aisle preference...),and no seat map available, while the A321 has plenty (including many extra legroom seats).
Why is that, and is there anyway of choosing a seat / paying for a seat, or only when online check in opens?