The six 707s Pan Am used to launch jet Transatlantic services in 1958 were domestic 707-121 models with JT-3C engines hence the occasional need to refuel en route... they also had 'interesting' experiences like a possibly supersonic dive over the Atlantic and losing an engine pod over Northern France, same airframe, both incidents, without injury fortunately..
https://abpic.co.uk/pictures/view/1178049/