I copied and pasted this text from the FB scheduling group a few months ago. I refer to it a lot, as it is impeccably described.


"A GS with less than 18 hours to report (F code) doesn’t necessarily have to actually report less than 18 hours from time of award. It is for any GS that the reserve is otherwise (contractually) ineligible to report for.

"Say someone is on day 1 so the earliest they can be made to report is 1000. 2 days out they can get a GS “with less than 18 hours to report” that reports at 0800 on that first LC day. Same with a pilot coming off a vacation day who otherwise can’t report before 1800. In all those circumstances the first duty period will pay above reserve guarantee with no PB days. If the trip subsequently interrupts an X day then the standard GS/PB days apply. Outside if the whole rotation is on LC days then it’s only the first duty period that pays extra."