With PanAm, we had spare engines available at strategic locations.
If no spare engine, we had agreement with other airlines etc.
We also had potentially spare airplanes available for the convenience of passengers.
Trying to minimize delays, and problems for hotels and connecting flights.
xxx
Of course, the final decision as to what and where was with the captain.
But we had to call operations, discuss the situation and options, and take the best.
However, I doubt PanAm did continue for an oceanic flight and destination 10 hrs away.
The 747 is ok on 3 engines, if another fails same side, still ok, but requires landing nearest suitable airport.
xxx
I do engine-out ferries on 747, I have done 3 of them in my career.
There is no V1 speed
per se on a 3 engine ferry.
You pray your 3 engines are ok to reach Vmca-2 (160 Kts) and 400' AGL.
Engine-out ferries training is part of our normal recurrent simulator training.
Most captains are qualified to do engine-out ferries, our airline policy.
xxx
Happy contrails