At PSA, you bid for lines. There may be 80 pilots bidding for 62 lines, so the first 62 guys in seniority order will be awarded a line. That's Round 1.

After Round 1, we can adjust our schedule during the Schedule Adjustment Period (SAP). Look at the SAP thread for details. Some pilots will drop trips, etc.

After SAP, Round 2 bidding opens. Crew Scheduling will make more lines with the trips that were dropped during SAP or from those who had training, vacation, etc. Round 2 is also when you bid for reserve lines.

After Round 2, you can do Seniority Based trades. If there are more reserves than required on the days you don't want to work, you can trade with trips in Open Time. The requests you submitted will be awarded in seniority order.

After Seniority Based trades, First Come First Served trades open. Like the title implies, it's first come first served. Trade approvals also depend on the reserve grid.