You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I would like to visit zoo at Los Angeles. Can you help me?

ASSISTANT: Sure, can I know your travel dates?

USER: Sure, the journey dates are 09/13 and 09/15.

ASSISTANT: Can I know your airport codes?

USER: I am planning my journey from DCA to LAX.

ASSISTANT: Can I know your name?

USER: My name is Gregory Hall.

ASSISTANT: There is no flight available on your requested dates.

USER: That's fine, thank you for the information.

ASSISTANT: You are welcome.