Originally Posted by Baradium

Vacation doesn't have to be pre-assigned with PBS. I've worked at an airline previously that built a line and then just dropped any trips that conflicted with vacation. So no, with PBS it is not that it "would be" pre-assigned. It's just that most airlines operate that way because there are some benefits.

If you build lines and THEN drop trips for the vacation interference then you end up with some senior trips in open time after line construction that would have helped junior bidders' schedules. This can have a larger impact than you'd think because it cascades as each bidder starting with the next one below the first pilot with vacation has a larger trip pool. If you set it up to pre-award vacation then those trips are available for other lines and helps everyone's schedules whether they have vacation or not (and it can have a large impact). By giving a high enough bid credit for vacation in PBS you can make for better schedules in vacation months without having to build in conflicting trips. Another thing some airlines have done is allow an option to pre-assign a day off before or after vacation (or both) to ensure you can guarantee a minimum of 9 days off in a row if desired.

I don't work for Alaska, just wanted to makes sure there's not misinformation out there. The biggest thing about PBS is making sure that the contractual rules surrounding it are appropriate. Done right it can be a massive QOL boost to pilots while making scheduling easier for the company.