A friend of mine recently booked a multi-city one-way ticket covering three airlines that according to ITA Matrix includes this mysterious segment:
Note that this is described as "First (F)", even though Jetstar is a low-cost carrier, doesn't offer more than Economy and Business, and their GDS guide doesn't recognize a fare class "F". The rest of the itinerary is also all "Economy (S)", which is a Starter Plus fare.
Any idea what kind of seat she's actually going to end up in, and how this happened?