I have dispatched so many airlines and I can promise you that ALL airlines including people such as ryanair to the big boys aka VS/BA run positioning flights. These are for various reasons....some operational (i.e crew shortages) and occur infrequently...many others epecially the charter bunch operate dozens of posn flights! I don't hear them getting shot for it!?
True at all LON bases we are short of crew because of the 900 rules and at LGW around 35% of the base is on restricted rosters (including myself)!