You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you?

USER: I am Gary Davis. I am planning to attend a board meeting at DEN. Can you book a flight ticket from LAS?

ASSISTANT: Sure, may I know your planned travel dates to check for the flight availability?

USER: I will start on June, 9 and return back on June, 11.

ASSISTANT: Do you have any specifications?

USER: I need a connecting flight and make sure that my depart time should be at evening.

ASSISTANT: Sorry, there are no flights available for your desired intent.

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

ASSISTANT: Thank you for reaching us.