You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I want to book a flight to DCA for vacation. Can you book a flight for me?

ASSISTANT: May I know your desired travel dates please?

USER: I will fly on Mar 27 and return on Mar 29.

ASSISTANT: Please share your source airport code.

USER: My source point is IAD.

ASSISTANT: May I know your name please?

USER: My name is Kenneth Allen.

ASSISTANT: Do you have any specifications?

USER: I prefer a connecting flight.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: Ok, thank you for the information.

ASSISTANT: Thank you for opting us.