I'll apply a little chainsaw math to this. The "G Line" (Junior guaranteed lineholder) runs to about 85% in my BES, so I'll assume it does roughly the same for others. Below the "G Line" some lines are awarded, but not in seniority order and you definitely can't count on them, even if you're the first one below the line. Basing it on those assumptions and generalities, roughly the bottom 100 pilots in the 650 pilot IAH 737 FO BES are on reserve.

A minimum of the top 25% must be offered long call (A) reserve. That means even if half of the top 25% of reserves want short call (Four hours more pay), none of those unused long call slots are guaranteed to trickle down to the bottom 75% contractually (They're use 'em or lose 'em).

Don't know, but contractually they can assign you a short call period to begin nine hours after contact.

Using 350 pilots in the BES, roughly 50.

The vast majority, I suspect.

David posted between my response and he's in the BES giving you actual numbers. He's looking at actual monthly bidders, while I was just looking at staffing. I don't think, however, 25% of reserve lines are A lines, just they must be offered to the top 25% of reserve bidders.