[inigyou]

These ultralong flights will surely only be used regularly on routes with enough traffic, like London/Sydney.

Although they could also run intermittently to different places. Like London/Sydney on Monday, London/Melbourne on Tuesday... Which one brings in more money? I really have no idea. If you do it like this you can serve more people with direct flights, but they can't pick any day they want. I was once on a scenic long-distance train for some reason that didn't run every day due to low usage — Wellington to Auckland, I think? Normally you'd fly.