You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: Can you book a flight ticket for me on any direct flight?

ASSISTANT: Sure, please help me with your name.

USER: I am Jonathan Hernandez.

ASSISTANT: Thank you. Can I know your source and destination airport codes?

USER: I want to travel from DCA to AUS.

ASSISTANT: May I know your travel dates?

USER: My trip dates are 06/16 and 06/18.

ASSISTANT: Ok, is there any class preference?

USER: No, thanks for asking.

ASSISTANT: Ok, please wait for a while.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no flight available on your preferred travel dates.

USER: That's ok, thank you for your service.

ASSISTANT: You are welcome and have a nice day.