We have what we call the G-line. Which is the junior most person in each category that is gauranteed a line during bidding. Sometimes folks junior to that person will get a line, but the G-line person is the junior most that is gaurnateed a line if they ask for one. That is the criteria I used to determine who the junior lineholder was system wide and that person was a LAX 737 FO for July.

In the actual awarding process folks junior to that person "can" be awarded a line based on the bidding patterns of pilots senior to them. This is especially true for those that you mention that have training or vacation in the month and therefore only need 1 or 2 trips to make a legal line. With that always being a possibility, it still remains that the only people that are gauranteed a line are those at or above the Gline that actually bid for a line.

Just checked August using the same criteria and it is again a LAX 737 FO that is the juniormost person system wide that is gauranteed a line. SFO 320 FO is second.