From 1953 through 1970, United offered men-only ‘Executive flights’ between New York and Chicago and between Los Angeles and San Francisco.
Flights mostly operated at 5pm in each direction between the two cities(generally six days a week excluding Saturdays). They didn’t just ban women, but children also, and flight attendants catered to these business flights with special meals and offered complimentary cigars.
One story has the airline issuing vouchers to business men to bring their wives with them along, so they could show them how safe flying was (a serious concern back then). They discontinued the promotion because they decided to start calling the wives after the vouchers were redeemed, and a bunch of them had never set foot on a plane.