Maybe Mr Groundloop as the airlines get crews through agencies and after a period they can then employ the guys directly..big saving .. or maybe because the work patten for summer/winter requires only xx crew.. or maybe because they can! I am aware of several AEU pilots that were on rolling six month contracts, this is quite normal.. and with respect.. if pilots have to be away from home/loved ones etc for these contracts they often only want 6 months so they can look around.. Lastly, the agencies sometimes only want crews tied up for six months so they can renegotiate. A few years ago some of the Man AEU crews were on temporary release from Lingus and you may find this is the route they have to go down to get A320 crew as well. Feast or Famine