Airline programs have structured curriculums approved by the FAA. While there is room to add extra sessions when needed, there are limits to how many extra sims may be offered based on performance evaluation and progression. If it is apparent that extra sims are not really helping then there comes a point where the airline has to pull the plug.

It is unlikely that a candidate will be asked to resign. The conversation would probably relay to the candidate that they will not be able to successfully complete the program and therefore will be dismissed. As a saving grace, the option to resign is considered by the candidate. Future employment prospects depend on how the candidate is able to clearly explain the circumstances and what they learnt from it.