Dan Dare
I suspect that the origins are 'trooping' service personnel. This leads me to Marshall Suttons of Beverley in Yorkshire who ran charter in connection with Dan Dare. I had/have a villa in Menorca for 35 years and used MS and Dan Dare. So there is Newcastle, Bristol, Manchester, Teesside, Birmingham and - guessing- Cardiff.
In a Quixotic way, Menorca 'changeover days' were fridays and then Fridays and Mondays so Dan Dare must have flown to other destinations.
I do recall flights flying 'w's' then.
I hope that my sketchy memory will start to give clues to your quest.