You are quoting a lot of distances, would you kindly expand on if you mean great circle distances, Still Air Distances of ESAD? It makes quite a difference
Yes, it does mean great circle distances. Which is why I felt the need to remind that LAX-MEL westbound and SFO-HKG westbound were considered problematic - likely headwinds.
Singapore has A340-500 struggling on SIN-LAX (14100 km) and SIN-EWR (15 400 km) Why do you say that its struggling?
They wanted to have full three class service on the route - over 200 seats total, real economy, business and first class - and were disappointed to find that they could not, and had to make do with just 181 seats, Executive Economy and no First. Eventually, even this was too much, which is why they are dumping the Executive Economy altogether, and going to mere 100 seats (but still no first class).