970km one way is very long for a helicopter. That's the reason they didn't use one in this case. I'm not sure if there are any helicopters to this day that will do 2000km without refueling.
Helicopters these days can at least get one way, so the simplest solution today would probably be dropping return fuel from a cargo plane or doing in-flight refueling of a helicopter.
If you have enough equipment, you can set up a relay where tankers themselves get refueled by other tankers. This can dramatically extend the range of a small number of aircraft, though the logistics (and expense) gets out of hand quickly.
The British did this during the Falklands War in 1982. In Operation Black Buck, a bomber from Ascension Island (near the equator), attacked Port Stanley Airport (~52°S, about 12000 km away). To do so, the bomber was refueled 7 times on the way out (and once on the return), while a fleet of tankers refueled each other 9 more times. Wikipedia has a diagram showing how this worked: https://en.wikipedia.org/wiki/Operation_Black_Buck#/media/Fi...
Is that equivalent to the 'rocket equation', where each tanker is analogous to another stage on the rocket? (You spend increasing amounts of fuel to get the fuel out to where it needs to be transferred in to be then burned.)
Seems very similar to me, though the constraints are a bit different: you want the tankers back, presumably, but you also don't have to move all of it together
I don't know if this was done, but it's totally possible to get a helicopter to carry a tank of fuel and leave it floating midway in the ocean (or on ice strong enough to land on).
You can then go back, refuel, and this time go the whole way, stopping off for fuel at your new midway point.
You just need to make sure you don't forget where you put the fuel!
Helicopters these days can at least get one way, so the simplest solution today would probably be dropping return fuel from a cargo plane or doing in-flight refueling of a helicopter.