Supply and demand
You can allocated any fleet anytime and what you think you may get on arrival could change although does not happen very often. Some 320 guys arrive and get 330. Some 330 guys and get assigned 320. This is very rare, but could happen and is mentioned in your contract offer that fleet allocation change could happen due to demand and needs at the time etc etc. All depends on fleet needs at the time and you, what hours you have etc etc. If the fleet allocated is more important to you than the company offering you the job, maybe you're coming for the wrong reasons. And just to add, although it's known the 320 fleet works hard, don't be fooled into thinking other fleets are holiday camps. You work hard on most fleets and some have plus and minus points about them. One last point, some here on the 320 fleet are very happy and don't want fleet change, so don't believe everything posted here.