You can apply for NCC recruitment from 20 to 24 years (at the time of commencement of course). And the Upper age limit for Candidates holding valid and current Commercial Pilot Licence issued by DGCA (India) is relaxed up to 26 years(at the time of commencement of course). And the number of attempts can be calculated only if we know the exam number of times the recruitment arises. But as per Afcat it's 2 per year.