Originally Posted by
intuition
Because ITA matrix sees phantom availability. It suggests a PNOBAG-fare on the ATH-LON leg, but only full fare Y is available on that flight. So the price qouted is not bookable.
Your outbound is easily booked on A3 website as a oneway, I suggest you look for another date or route for your return.
Thanks! I can book BA on the return for total £238 per person, still not bad.