I was of the understanding that airport companies have to look outside their organisation under the rules of employment law anyway.
No they don't, in fact many companies have either Company policy or Union agreements that all vacancies are initally advertised internally;
a) It's a good incentive for anyone wanting to improve themselves and/or, moving into a job they've always wanted to do.
b) It saves a lot of money and possibly time wasted, when the person you want is already sitting on the doorstep waiting to get in.
c) Internal candidates are often known quantities. Whilst not always the case, they are often a better investment when it comes to further training.
More and more, airports will stick to recruiting for such positions from within, only when the internal candidates prove themselves not to be up to standard will they look outside and then, it's highly likely that the winning applicant will be local.