"Par Avion" is the 12th episode of the 3rd season of Lost and the 61st episode overall, making it the exact midpoint of the series. It was aired on March 14, 2007, on ABC. The episode was written by Christina M. Kim and Jordan Rosenberg and directed by Paul Edwards. The character of Claire Littleton (Emilie de Ravin) is featured in the episode's flashbacks.

The episode opens with a Claire Littleton flashback. Claire finds herself in a ruined car. She sees her mother, Carole Littleton, lying in the road, badly injured. At the hospital, Claire's Aunt Lindsey confronts Claire about her being cleaned up. A doctor tells Claire all her mother's medical expenses have been taken care of by an anonymous person.

Later, Claire discovers her mother has a visitor, Dr. Christian Shephard (John Terry). She realizes he is the one paying the hospital bills, and asks who he is. Reluctantly, Christian admits that he is her father, meaning Jack and Claire are half-siblings.

Later, Christian explains over coffee with Claire that he had a fling with her mother which resulted in Claire's birth. However, Claire's mother did not like that he had another family and told him to stay away. He reveals that the reason he wanted to talk with her is that he wants Claire to think about ending her mother's life. Claire gets angry, believing that Christian is there to "correct a mistake" he made by having Claire with her mother. Claire tells him paying the bill does not make him noble and leaves, after telling him she does not even know his name, and does not want to know it.

Back in Sydney, Claire visits her mother, who is still in a persistent vegetative state. Although still in a coma, Claire reveals to her mother she is pregnant but giving away the baby. She tearfully apologizes for the accident and for all the terrible things she said to her in the car before it happened.

Desmond Hume (Henry Ian Cusick) suggests that Charlie should go boar hunting. Claire sees a glint in a flock of seagulls. Claire realizes that the birds migrate, and that they may be tagged. She decides to capture a bird and attach a note about the crash of Flight 815 and the survivors, hoping that someone will find and read it.

After explaining her plan, Jin-Soo Kwon (Daniel Dae Kim) and Sun-Hwa Kwon (Yunjin Kim) help Claire set up a trap to capture one of the birds. Just as Jin is about to spring the trap, gunshots ring out and scare the birds away. Desmond emerges from the jungle, claiming he was on the trail of a boar. Claire knows it somehow involves Charlie. She confronts Charlie about his and Desmond's strange behavior. Although Charlie struggles with whether to tell Claire about Desmond's prediction, he instead says her plan will only give people false hope. Claire is angry and asks Charlie to leave her alone.

Claire, after seeing an argument between Desmond and Charlie, follows Desmond. He picks up a seagull from a rock and explains to Claire how he's seen that if Charlie had gone to get the bird, he would have died after falling into the sea. Claire takes the bird to Charlie and tells him she knows of the visions. Charlie and Claire release the bird, with a note explaining the circumstances of the crash.