I must disagree with the above post. 33 is no problems at all. I got my first commercial job at 36 and I am now a training captain with a small regional. I am just about to do line training with a guy who is getting his first commercial job and he is 43! I know of several similar stories.
Regarding being taken on by the big boys, it does not seem to be an issue at the moment. There is increasing recognition that many people now come into aviation later in life due to financial constraints and so on. The fact is that on a seniority list you will not make the very top but you can still have a fantastic career ahead of you. I spoke to someone last week who has just got a job with British Midland on the Airbus at 48! He is a First Officer from a regional with 2000 hours total which is way less than someone of his age should have.
Both myself and others like me are starting to get interviews from large jet operators so all is far from lost.
Hope that gives you some idea. As we all know getting that first job is always a bit tricky but once you are there then the world is your oyster etc etc..