Extra pre-XMas flights?
 

I was shopping for the IAD-PDX nonstop for December 22, and discovered this tidbit: instead of the usual A319 flight (UA251), there was also UA1401, which is a 757 flight. It looks real, but since it doesn't exist on the prior or following day I wonder, is United tossing in a few extra flights around the holidays? Is this routine?

It's quite possible to meet projected additional demand around the holidays. The opposite could also be true (fewer flights on actual holiday days when people are less likely to fly).

There's also an extra PDX-IAD (a redeye) on December 22:

UA1402 PDX 11:59PM IAD 7:42 AM +1 752 4h43m

I'm not seeing any other extra Christmas transcons at this point, though. Anyone know why PDX was so fortunate?

1,000th post! :)

Definitely known to happen - I spend Christmas in Hawaii with my family, and there is always an extra red eye on OGG-SFO during the holidays. Where the extra plane comes from, I don't know.