You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: I am looking for a flight from IAD to LAS, can you help me in booking?

ASSISTANT: Sure, please provide your itinerary dates.

USER: Sure, my planned travel dates are Apr 19 and Apr 21.

ASSISTANT: Do you have any specifications?

USER: I prefer for an economy class.

ASSISTANT: May I know your name?

USER: Myself Larry Williams.

ASSISTANT: Please give me a moment to check for available flights.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry Larry Williams, no flights are available on your route.

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for reaching us.