Originally Posted by CA1900

Just to add onto what they said about the "Green bases," they mean only one thing: You can bid for the less-than-7-day-tour schedules. The "Crew Choice" schedules, where your schedule changes month-to-month, are available with a maximum of 8, 7, 6, and 5-day tours, with various limitations that are too complex to get into here. But the 5-day- and 6-day-max schedules are only available to those who are in the "green" bases. All of the other schedules are available at any base, including the 7-on/7-off.