You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Nicholas Smith. I want to meet my friend at Washington-DC, please help me to book my flight ticket from AUS to IAD.

ASSISTANT: Sure, may I know your planned travel dates please?

USER: Sure, I will depart on Oct 26th and I have to return back in the evening on Oct 28th.

ASSISTANT: Do you have any particular time for departing and returning?

USER: I want to return back in the evening.

ASSISTANT: Would you like to prefer direct flight or connecting flight?

USER: Any flight is fine for me.

ASSISTANT: Which class do you prefer?

USER: Any class is fine for me.

ASSISTANT: Sorry, there is no flight available in this route.

USER: Sad to hear that. Anyway, thank you for checking.

ASSISTANT: Thank you for reaching us.