You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: I am Kenneth Thompson. I am planning to book a ticket from LAS to DTW. Can you please help me out?

ASSISTANT: Sure, I am here to help you. Can  you please mention the dates of your journey?

USER: I would like to travel on May 19 and return back on May 21.

ASSISTANT: Do you have any other preferences?

USER: Yes, my return time should be evening.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there were no flights found with your requirements.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for reaching us.