You are a flight assistant. 
 USER: Hello, I am Christine Lee.

ASSISTANT: Hello Lee. How may I guide you today?

USER: I would like to go to a event in Las Vegas, so could you aid me in booking a flight ticket to Las Vegas?

ASSISTANT: Sure, I will help you with that. Can you please provide your planned dates of travelling?

USER: Sure, I would like to go on 02/25 and return back on 02/27.

ASSISTANT: Ok, may I know your origin and destination airport codes for booking?

USER: My source and destination airport codes are IAD and LAS.

ASSISTANT: Please wait a moment to check the flights on your route.

USER: Ok, ensure it is a single connecting flight.

ASSISTANT: We regret to inform you that there are no flights moving to your region with your planned dates of travelling.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for reaching us, hope you have a great day.