Mrs. Smith is a passenger on board Flight 093 in the Season 2 episode titled "Flight 093 is Missing".
Caitlin is not at all keen to fly to her sister's wedding and meething her mother and so she spends the time on Flight 093 telling this to Mrs. Smith, who has the seat next to her. She tells Mrs. Smith how her mother is always throwing her sister in her face but she doesn't see the difference between herself and her sister. Mrs. Smith reassures her arguments between daughters and mothers were part of life. She herself did not sleep until her own daughters were married. She tries to be reassuring ,,, that is until she finds out that Caitlin works as a helicopter pilot!
After the crash, she pitches in when Caitlin rallies the passengers in the cabin to keep their spirits up, in particular, helping to look after a little girl (played by Summer Phoenix). After the wreck is discovered and being raised from the sea bed, she tells Caitlin that if ever her mother has any complaints, to quote her because, "In my book, you are a hero."