I should say that is a good question. But decisions like these are made by the HR taking the working environment into consideration and it is not just applicable to airlines and pilots but all organizations hiring fresh talent as FRESHERS. What the company requires is how best a person, if selected, can adjust to the working environment and how enthusiastic is he to learn more to contribute to the growth of his career and also to the organization. And a fresher at that age would definitely not feel comfortable working under more experienced people who might be much younger to him. And also it is the experience which counts more than age and hence people who have more than 1000hrs on any aircraft and probably a TR are allowed to apply till 40 yrs of age. Reason being they are experienced and would not feel so incompetent to work in a dynamic environment.