You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I am planning for a vacation at Washington with my family. Can you book a flight for me?

ASSISTANT: Sure, let me know your planned journey dates?

USER: I will fly on Sept 02 and return on Sept 04.

ASSISTANT: Do you have any connection limit?

USER: I prefer a connecting flight.

ASSISTANT: May I know your airport codes?

USER: My source point is SFO and destination is DCA.

ASSISTANT: Is there any other specifications?

USER: No.

ASSISTANT: Can I know your good name?

USER: My name is Donald Allen.

ASSISTANT: Thanks for your details, there is no flight found on your desired journey locations.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for availing us.