You're not 'locked in' to CitiExpress, no, also re:
"Yet have job offer before you start training"
No you don't. It's a crock o'sh*te. Try getting a letter of intent off them before you start, or any sort of vague written confirmation. It won't happen. At the end, if they're in the mood and have spaces you may get priority over Joe Bloggs, but the airline is under no obligation whatsoever to offer you a position even if you come top of the course and pass everything first time with flying colour, they can just walk away and leave you jobless.