Originally Posted by
rickair7777
You do not need any flight training at all to take the written exams.
But I think you need a PPL license to take the CPL written, and a CPL to take an ATP written. Not certain about that.
For the ATP ME you must complete the ATP CTP class which includes 10 hours of simulator time, 6 hours of which are full motion so that is "flight training." There is no requirement to hold the lower grade certificate to take the knowledge test for the next level certificate. The only requirements are that you have an instructor's endorsement (except for the ATP) and that you of an age where you would reach the minimum age for the certificate before the written test expired. So you have to be 16 to take the commercial written.
You do have to hold the next lower certificate to take the checkride for a higher grade certificate.