I think most airlines with permanent contracts will require you to work full-time first and then give options on part-time. I'm on my 4th company and either I have or know someone who has has a part cum flexi contract, but they've always worked full-time initially.
I'm welcome to be proven wrong though! As previously mentioned it's probably more likely if you've previous experience as it takes a little while for the SEP & service for each airline to filter through!