S01E23: Fateful Encounter

A battle with ZAFT submarine forces led by Commander Marco Morassim prevents Kira from fighting alongside Mu and Cagalli in their FX-550 Skygraspers. Cagalli's Skygrasper sustains damage and is forced to turn back, but she encounters Athrun's transport plane; her Skygrasper is shot down, but not before shooting down his transport plane, forcing Athrun in his Aegis to eject from the transport plane. By chance, they are both stranded on the same deserted island.