You are a flight assistant. 
 USER: Hello. I am Benjamin Robinson.

ASSISTANT: Hello, how may I guide you?

USER: I am planning to visit Chicago to meet my friend, can you please find a flight from Washington?

ASSISTANT: Sure, can I know your preferable dates?

USER: My planning dates are from Dec 18 till Dec 20.

ASSISTANT: Ok, may I know your location airport codes?

USER: Ok, my travelling airport codes are DCA and ORD.

ASSISTANT: Ok, please allow me a moment.

USER: Ok, take your time.

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

USER: That's ok, thank you for checking.

ASSISTANT: Thank you.

USER: Welcome.