We had to transfer a few 10GBs, if not 100GBs between Europe and the US back 15yo.

Bandwidth was of 100KB/sec at most, I suggested to do that fly over things if the systems team didn't want to raise the priority of that transfer, after prod tried 3 times over the weekend, sadly, they changed the priority of that flow, it took still like 40h? For the initial load.