Line bidding advantage is vacation conflict. It used to be any trip that dropped you got paid for and never had to add back a trip. After the Kasher arbitration of 2005 (? I think), we lost that. So now if you have 5 vacation days that pays 17.5 hrs and you drop a 24 hr 4-day trip, you are net down by 6.5 hrs. Now you got to look at your overall line value. It must stay above 75 hrs. So if your original line was 82 hrs, minus 6.5 you're still okay because you get 75.5 hrs. But if your original line was 75 hrs, now you're minus 6.5 hrs for a new total of 68.5 hrs. You must now add back at least 6.5 hrs in step trading to get your line back above 75 hrs. In a nutshell, in a vacation month, you have to stay above 75 hrs.