Presumably they get away with the advert because flying really was predominantly a male career in those days, though there were plenty of women pioneers (Amelia Earhardt, Hanna Reitsch etc...) who flew recreationally or to break records, and whose skills were recognised in their own time. It would have been silly if they'd rewritten history to have a woman pilot carrying passengers on the Rapide, though it wouldn't have hurt them to shown a lady flying the more modern airliners.
My impression is that aviation isn't as enlightened as it sometimes seems to think it is. There's certainly a fair amount of sexist banter in club rooms, though probably most female pilots don't get to hear much of it.
Interestingly, I get the impression that there's now quite a high proportion of female commercial pilots coming through training, whereas relatively few women seem to train for a vanilla PPL. It would be interesting to see some numbers.