When PBS awards trips, if there are a large portion of trips left over on a particular day (July 4th, Txgvng, Xmas, etc), the company will ask to go up the seniority list from the bottom until they have found enough junior pilots who were originally awarded the holiday off to cover these left over trips.

My understanding is that the company then clears everyone's schedule from that point down and reruns everyone's preferences with the exception that the holiday trip is awarded first and then all of the other preferences are considered. I think this is only allowed to affect the bottom 50% of any one group.

As I understand it, the company demanded to use this feature in April and May and were firmly told no. The union did approve it's use for July but I haven't heard anyone complain about it and there's been no official mention of it being used.