A possible approach that would involve a court case:

In most states (AFAIK...it was where my airline was based though) company's are not allowed to recoup training costs (pay for training, training bond) if that training is required to perform the work you were hired to do and you were hired without bringing it with you. So, you could make the case that probationary pay (especially at like, Continental!) is in effect a recoup of training costs...

Spongebob