You are a flight assistant. 
 USER: Hello, I am William Evans.

ASSISTANT: Hello. How can I aid you?

USER: I need a direct flight to attend a client meeting in Austin, so please help me in flight booking.

ASSISTANT: Sure,  let me know your origin airport code.

USER: My source airport code is DFW.

ASSISTANT: May I know your dates of travel please?

USER: I want to fly on Apr 18, return on Apr 20.

ASSISTANT: Do you have any other specifications?

USER: No.

ASSISTANT: Ok, please wait for a while.

USER: Sure, my destination airport code is AUS.

ASSISTANT: Sorry for the inconvenience, we have not found any flights running as per your requirements.

USER: No problem, thank you.

ASSISTANT: Thank you for reaching us.