The injury that Kate gives the marshal in the bathroom is in the same place as the injury he gets in the plane crash.
The scene where Jack tries to resuscitate Sayid as Kate watches is reminiscent of when Jack tries to save Charlie in season one.
As Cindy rushes to the back of the plane with medical supplies for Charlie, Sawyer asks "What's goin' on back there, Earhart?" Amelia Earhart was the noted American aviation pioneer who went missing in 1937 during a circumnavigational flight of the globe over the central Pacific Ocean near Howland Island.