I think if I were going to challenge this I would look towards using EU age discrimination legislation. In general throughout the EU there isn't a formal retirement age any more and you cannot discriminate on the grounds of age. As far as I know pilots are the only occupation with a retirement age in law.
Its interesting also that you can be driving a public bus at any age with only a basic medical and that's single crew.
Another anomaly is that in the U.K. I cannot claim my state pension until I'm 67, yet I'm forced out of work at 65. All theses I would have thought are interesting areas to explore.