You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I want to book a direct flight to attend a business meeting at DEN, can you help me with booking?

ASSISTANT: Sure, I am here to help you out. May I know your travelling dates please?

USER: I will fly on Sept 28 and recur on Sept 30.

ASSISTANT: Can you please share your destination airport codes?

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

ASSISTANT: Can I have your name please?

USER: I am John White.

ASSISTANT: Do you have any other specifications?

USER: No.

ASSISTANT: John White, there are no flights available in your route.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for choosing us.