in captain america: the first avenger and agent carter, howard stark has a new yorker accent, but does not have one in iron man 2, ant-man, or captain america: civil war.
real world reason for this: howard is played by different actors in different time periods, and no one probably cared that much.
possible in-universe reason for this: howard deliberately lost his accent to appear more respectable and be taken more seriously as he got older and went from a playboy to one of the most powerful businessmen in the world. in other words, he SOLD OUT and is a FAKE MOTHERFUCKER.
no but for real when did howard stark stop trying to be howard hughes and start trying to be walt disney?
probably around the time that hughes’s ocd started to consume him while disney started to become king of american capitalism now that i think about it