You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. How can I assist you?

USER: Could you please help me in booking my flight ticket?

ASSISTANT: Sure, could you let me know the airport codes?

USER: Book my ticket from my current location to DC - DCA. My current location is MI - DTW.

ASSISTANT: Let me know your travel dates?

USER: My journey starts from 10/19 and will return on 10/21.

ASSISTANT: Is there any additional requirements do you want to know? Can I know your name?

USER: No,let me know if the flight is available or not. This is Melissa Nelson.

ASSISTANT: Sorry Nelson, there is no flight matching with your requirements. Thank you for your time.

USER: OK. Your welcome.