You are joining an Airline, not a fleet. If you do not understand the difference you should stay where you are.
To quote from another thread..
I'm now 3 weeks into my course and the mantra throughout the company is "seniority is everything". You are joining a company not a fleet so just take whatever you are offered, get in the front door and you can move around later till your heart is content - the date you joined the company means everything - not the date you join a particular fleet.