The one bit of confusing information here is the flight.
The original booking was from Oslo to Seattle return, via Frankfurt each way.
The passenger actually flew to Seattle!
On getting nearly all the way back to Oslo, at Frankfurt the passenger chose not to continue the journey, the last little bit to Oslo!
Is it actually cheaper to fly all the way from Oslo to Seattle and back to Frankfurt than it is to fly on a single direct Oslo Frankfurt ticket?
The Guardian says the passenger subsequently purchased a Frankfurt Berlin ticket. It still makes little sense if the goal was to fly from Oslo direct to Berlin.
Is the answer here that the passenger originally intended to fly to Seattle. Having been to Seattle the next destination was genuinely Berlin.
On international flights there can be substantial savings on a return flight compared with separate destinations. Hence a ticket Oslo to Seattle plus a separate ticket Seattle to Berlin is being compAred with the original Oslo to Seattle return ticket.
Aside from the time saving how much did the traveller save in costs by simply not staying on the flight back to Oslo? The difference or saving is a Frankfurt to Berlin airfare vs Oslo to Berlin. True, Oslo is further.
I have yet to find a current example (casually testing a few likely flight choices with Qantas) of where this strategy may provide a benefit for domestic Australian travel. The milk run flights (same flight number all the way) I am most familiar with rarely offer specials. They make the money out of filling the hops. Where they fly in Qld or NSW it is always much lower cost to fly to the end destination direct on a big jet than the slow way.
In looking at multi leg flights where the flight flight number changes, I can’t recall ever finding special deals where it was cheaper to fly to a regional centre via a Capital than to the Capital direct on the same day at about the same time.
Literally @BrendanMays, the headline proposition is about an Australian passenger being sued because they cancel a flight. I’ve cancelled a number of flights, one very recently. It was not a problem. No risk of being sued. Just a loss of fare and no claim on travel insurance because the reasonable causes are all excluded!
To align with the European example, the real question may be, ‘ can an airline sue a passenger on an Australian domestic flight for failing to board and not continuing on a latter leg after commencing a journey, when travelling with only carry on?’
The European example appears to be more complex than a simple two leg example. It is also an international flight example. If I had a need to fly from Cairns to Melbourne for a long weekend, then be in Brisbane for Tuesday for work.
Would it be possible to purchase a weekend special which changes flights in Brisbane, cheaper than the alternate two flight booking, or multi leg booking?