1. Company gets flying from UA. Company and Alpa generate line solutions, one solution gets selected.
2. Lines are published for each base. Bidding opens. If you are senior enough to hold a line, you put in a bid for a line in your order of preference, then you are awarded a line based on your seniority after the bidding closes.
3. The ILIW then opens for you to improve your line a few days later. All but 8 days are set at +4 for coverage. Those are days you can drop flying off of your line down to 60 credit hours if you desire. First come, first served. Be quick at the opening of the ILIW.
During the ILIW, trading occurs as well as drops from individual lines. There is no set order to what transpires after the window opens. I have traded my entire month of flying (and dropped a pairing or two) at the initial opening more than once and been successful. Usually I end up with more days off, more credit hours, and different days off.
Make sure you are off duty on the day the ILIW opens if you need to improve your line for the next month...