When I was doing my Faa CPL license in USA I had instructors with +35 years old and 500 hours, after they got 1500 hours or so, all of them began to work in regional and mayor airlines. But USA in aviation terms is almost another galaxy.
I lived in Spain, here people gets hired in the mayors whith as little as 22 years old (but you need something we call "godfathers" to get the job, that is someone that clears your path to get a flight deck position above the rest of the candidates, you know what i mean), in other hand, when you get older than 30, you began to be less attractive to the airlines (of course i´m talking about someone without godfather).
Iberia for example, rejects candidates after the interview with +35 (aprox) and little flight experience, they´ll never tell you that reason, but is a fact.
Too little jobs, too many candidates with too many "godfathers", if you are handicaped with your age makes everything far more difficult.