In the *A system (and others), partner are allowed to take some time to confirm flights and potentially refuse the request. UA is acting as a "travel agent" and has limited powers. Normally partner flights reconfirm quickly but there has been a strong response to the sale and possible inventory got oversold thru the various sources. The
The dropping of the BRU-ZRH would cause a repricing at today's prices (or changing to BRU-EWR) BUT it is worth pushing back and seeing if the agent can get a waiver from a supervisor / fares desk. The Twitter team is a good approach