You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you?

USER: I am Elizabeth Parker. I heard that Washington is a best place for site seeing, Can you please book a ticket on 09/21?

ASSISTANT: Sure, may I know your airport codes?

USER: Source code is Chicago, ORD and landing point is Washington, DCA.

ASSISTANT: Can I know your other date of travel please?

USER: Return is on 09/23.

ASSISTANT: Sorry, there were no flights found on your route.

USER: No problem. Thank you.

ASSISTANT: Thank you for opting us.