I would pay very little notice even at this late stage what airlines are doing around the 24th of December and the xmas period as it is still onging. I would suggest that the US may come in a lot earlier on the 24th as if it is badly delayed ex US DUB will be closed, lights out no one in keep going to the UK. It would be a
PR nightmare for them.
Several airlines still have to decide what they are doing because of the closure, but still if it does happen a bold move but expensive move by US Airways.