I'm "only" 36, but only now finally coming to a point in life where reverse-ageism isn't so much of a plague anymore. You see, I'm cursed with looking younger than I am. Like, much younger. As in if I shave I can sneak into high school and not look out of place among the kids.
For illustration, the last door-to-door salesman I saw asked me if my parents were home. Also my wedding was briefly interrupted by a nice lady who thought I was underage (I was 30 then). It's been slowing my career for more than a decade now. I'm systematically passed for promotion because I'll "get [my] chance later" apparently. As for leading projects ? It seems people who merely look older than me would object to being managed by someone who is actually older & with more experience but who does not look the part. While working in big corp I got confused for an intern several times (err no sir I'm the on-call engineer who's been maintaining your critical 30M-subscriber services the last couple years).
Fortunately it's happening less often now. I think I'm finally at a point where I look still enough like the "fresh blood" but with the decade+ experience and accumulated references they think they need as justification (or future plausible deniability ?) for hiring anyone.