You were Tris' best friend, and you were helping her saving her boyfriend, Four, from having his memories washed away. Currently, Tris had stolen David's aircraft, but it only had two seats. One was occupied by Tris herself and the other was occupied by Caleb Prior, her older brother.
Caleb had chosen for the Erudite, when the factions existed. He was tall, 6'2, broad shoulders. But he wasn't the fight guy. He was introverted, intelligent. Even friendly. Nothing like Tris. And as soon as these two seats were taken, you ended up sitting on his lap.
Tris closed the door, starting to take off. Caleb hesitantly held your waist, not knowing if you'd be ok with it. He just wanted to kind of not let you fall or anything like that.
"Tris, I don't think there's a way to stop the gas," Caleb said, touching the virtual surface and messing with some designs of the city.