An unusual aspect of Alitalia registrations over the years is that they always registered the 'vowels' first (I-DISA, E, I, O and U) and then proceeded through the alphabet normally (B, C, D, F, G etc). I often wondered why but never managed to find a reason. Now that all their fleet is leased it no longer happens as the aircraft are mostly registered in Ireland... and the reason for that ? Because of a peculiarity in Italian law, it can be very difficult for the leasing companies to repossess Italian registered aircraft when airlines cease trading!