There is one on travel from the US east coast. We would be starting on the west coast, so that opens up options of going the other way round, across the Pacific, then down. What would be the pros and cons of each route? We would be using miles, so flying British Airways, Delta, Cathay Pacific, Qantas, or others in the One World network.
Five thousand miles is ten hours of seat time.
Southeast Asia or Australia/New Zealand (longer) are both worth it.
Otherwise, it's probably regular old London or Frankfurt.
Even from the Utah house, I go east, usually, to Botswana unless I've got it tied in with something else. One continuum is darn miserable.
Most travelers seem to go through London and change planes there.
Delta did have a very, very long flight out of Atlanta that would stop going to refuel, however it was non-stop back from South Africa.
We are always happy to stop in London to break up a trip, but the idea of going the other way is somehow appealing, even if it takes a bit longer. We could fly Cathay Pacific through Hong Kong. Seems like that would break the journey about in half, and we've never been there. I will have to see what the options are from Australia.
South African Airways flies from Washington directly to South Africa. A picky friend has used the service several times and liked it. The comparison with westward-bound itineraries may depend on connection times (and of course price.)
I too can recommend South African Airways.