Joe Biden turned a commercial flight into a full-on meet-and-greet ... bopping around the cabin, greeting passengers, and even penning a sweet note for a young girl. A TikTok making the rounds on social media shows a girl, Cailyn , stunned the former prez is sitting just three rows behind her ... where he's seen casually posted up reading the paper. Looks like Joey B and Dr. Jill looked to be flying in biz class, and Cailyn couldn't believe she found herself chatting with 46. They even snapped