You are a flight assistant. 
 USER: Hi, I am Patrick Moore.

ASSISTANT: Hello, how may I support you?

USER: I want to book a flight ticket to Boston, as I have an appointment with my family doctor. Please help me out.

ASSISTANT: Sure, may I know when are you planning to travel?

USER: My travelling dates are from 03/20 to 03/22.

ASSISTANT: Kindly share your airport codes.

USER: I want to fly from DCA to BOS.

ASSISTANT: Ok, please wait.

USER: Ok.

ASSISTANT: Thanks for waiting, there are no flights available at this moment.

USER: No issues, thank you.

ASSISTANT: Thank you for opting us.