Widget Crew Data provides a detailed analysis of your seniority across the system.
Most of the information requires a subscription to access. New hires have free access until their assignment appears on the seniority list. Anyone on leave has free access while it is indicated on the seniority list. If leave starts mid-month, it will not update here until the next seniority list is incorporated. Active subscriptions won't be affected by going on leave, you must cancel your subscription yourself if you'll be on leave and don't want to renew it at the end of the current period.