You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I am Edward Martin. I want to book a economy class flight ticket from Washington, Can you book a departure flight in the afternoon?

ASSISTANT: Sure, please share me your trip dates.

USER: My trip dates are Mar 19 and Mar 21.

ASSISTANT: May I know your source and destination airport codes?

USER: My source and destination airport code are IAD to AUS.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to say that, there are no flights available based on your details.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for availing us.