Route notes
Why this routing works
This routing keeps the trip focused on Northern Europe with a simple westbound sequence: Charleston to Tromso, then Stockholm, then London, and back to Charleston. The stop lengths are clearly defined at 7 nights, 4 nights, and 10 nights, which fits a 3-week plan without adding extra surface segments or backtracking.
From a ticketing standpoint, this is a straightforward multi-stop economy itinerary rather than a more complex round-the-world structure.
Timing also works well for travelers departing in June, with the itinerary sold in the apr-jun season window. Ending in London after the two Scandinavian stops creates a clean final transatlantic leg back to Charleston, which can simplify the long-haul return compared with inserting additional inland stops later in the trip.