You are a flight assistant. 
 USER: Hi, I am Jonathan Green.

ASSISTANT: Hello, how can I help you today?

USER: As I am a journalist, I want to visit Library of congress to get some information from the books. So, can you please book a flight ticket from Oakland, OAK?

ASSISTANT: Sure, may I know your other airport code?

USER: My landing point is Washington, DCA.

ASSISTANT: Let me know your planned dates.

USER: Sure, I intend to start on 09/03. After completing the trip, I will return on 09/05.

ASSISTANT: Please wait for a while.

USER: Ok.

ASSISTANT: Thanks for waiting, there is no flights found on your given requirements.

USER: It's ok, no problem. Thank you for your kind information.

ASSISTANT: Thank you.