Honestly! Some employers will try anything.
Tell CityJet to get stuffed mate.
No Irish court will uphold such a contract if you state clearly that:
1/ You were not made fully aware of the implications of said notice period at the signing of said contract.
2/ You are unhappy/ unimpressed etc with the position and wish to terminate said contract within the 'notice' period.
I may well be wrong, but I always believed that any agreed 'notice' period was mutual under Irish law ( i.e. if they reserve the right to 1 weeks notice during first 3 months probation, then you only have to offer 1 weeks notice during same period)
Give IAPLA a call, they have plenty of experience in relation to this sort of nonsense, and won’t even charge you a membership fee if you were an ALPA member back in the US.....