I realize that Leia and Han got on each other's nerves in "A NEW HOPE". I also realize that Han had expressed to Luke, his minor attraction toward her. And he briefly flirted with her at the medal ceremony, at the end of the movie. But when did Leia and Han started harboring serious feelings for each other before "THE EMPIRE STRIKES BACK"? When Han returned to the base after being on patrol, he and Leia literally exchanged soulful looks before they engaged in one of their arguments. What brought about that exchange of looks at the beginning of Episode V?