Most everyone on here seems to be American so you may never get an answer to this question. In general, age doesn't matter for civilian flying and it is likely that many on here can relate a story of someone in their 50's getting hired by a Major "legacy" carrier. In your mid to late 30's you still have a full career ahead of you. In the US Military your age is over the limit for flying or at the limits and in need of waivers depending on the service. I'd stick with the civilian side.