 A flashback in season one that shows Jack and Ana meeting at the airport bar mentions their seats on flight 815; Jack sits in row 23 and Ana Lucia in row 42.In season 6 a part of the plot associates each number with a different character, each of them being a "candidate", according to the Man in Black, destined to become the new 'protector of the Island' in Jacob's place.Jack Shepard was number 23, as in Psalm 23, The Lord is my Shepherd (but 42 is associated with Jin Kwon at that point).