To add to what Busboy said, almost all airlines have people on LOA who are over 60 for various reasons. There are guys at pax carriers who have been gone for years still listed as L1011/DC-10/727 pilots. Each carrier is slightly different, but in general these pilots do not appear on what you and I see as the seniority list, but that list is basically an active pilots seniority list. That is one of the reasons it takes so long to 'verify' a seniority list in a merger, because the real list has a lot of extra folks on it.