You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: I am Sandra Hill. I would like to book a flight ticket SFO to IAD. I am planning to move 03/30 and return back on 04/01.

ASSISTANT: Sure, can I know your preferable dates?

USER: Please check for direct flights.

ASSISTANT: I am sorry, there are no flights available.

USER: Thank you.

ASSISTANT: Thank you.