Scoring high marks in NTS will only get you to the interview, what you say and do in the interview will determine whether you are given the job or not.
I dont know if aviation experience will have any bearing on the recruitement process but i did'nt know anything about aviation when i went for the interview and i still got the job.

When you go for the interview never speak in urdu and dont ever give wrong answers for simple basic questions which everyone should know the answers to , for example like a candidate was asked what is the spelling of khyber pakhtunkhwa , and another was asked peshawar is in which province to which he replied NWFP. I mean if are that stupid you dont deserve this or any other job. dont be a parha likha jahil. you guys get my point.