At AK we bid and are awarded vacation in 7 day chunks. After the awards we can trade vacation days 1 for 1 with fellow pilots (Cpts to Cpts and FOs to FOs). So, let's say your buddy was awarded vacation over the week of Thanksgiving and you were not. He could trade you the day before Thanksgiving (the 23rd) for one of your vacation days and then you could bid a line with weekends off with a 2, 3 or 4 day trip over Thanksgiving which would be dropped (because it touched your vacation day). Simply pick up a trip elsewhere in the month to get your credit back up. One vacation day just got you Thanksgiving off. This loophole is costing the company $ as it forces them to hire more reserves and offer more premium pay (150%) to cover flying over the holidays. With PBS you could be assigned a trip on Thanksgiving day (the 24th)...still honoring your vacation day on the 23rd. PBS also helps the company in "transition" from one month to the next. Under our current system, a carryover pairing (one that starts at the end of one month and continues into the next) can be used to knock pairings off of your schedule in the coming month...if there is a conflict. This is another good way to massage your schedule as you can pick something up elsewhere in the month. Again, this costs the company $ as they have to hire more reserves to cover the "dropped" trips or offer premium pay to entice folks to pick them up. At AK, PBS would be a $ saving "win" for the company. Not even touching the subject of "step" trading, there are a lot of ways to manipulate your schedule here if you know what you are doing...and it drives the company crazy. Does that make sense?