Picture this:

You have 1 week of vacation. Lets say it lands on September 10-17. You bid 60, so you have to bid 60 lines. One of your last choices (worth 80 hours) has 1 day of a 4 day(22 hours) on the 10th and 1 day on a 4 day on the 17th (22 hours). A real contract with real work rules would dump both trips and pay you line guarantee.

However, because of Alaska's outstanding work rules, your 7 days of vacation are worth 21.5 hours. Your awarded 80 hour line has lost 44 hours because of trip drops to 36 hours, and add on your 21.5 hours of credit, which puts you at 57.5 hours. You now have to rebid for open flying trips in 2 rounds, trying to find open trips to get you back up to the line minimum (75). If you can't, then scheduling gets to try and find things for you to fly. If they can't find anything, you get a chance to opt in, or opt out. If you opt out, you get paid 57.5 hours. All because you used your one week of vacation.

If you try and bid a reserve line, you can try to find a line that has 5 days that work over your vacation. Some have 6 days of a reserve in a row. Minimum is 12 days off for reserves. If for some reason, you end up getting a reserve line that has 5 days off over you 7 days of vacation, you don't get any extra days off. You now have 14 days off for your vacation month on reserve by using 7 days of vacation.