You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I would like to visit Washington to meet my sister. Could you please help me in booking a ticket?

ASSISTANT: Sure, I will help you to book a ticket. Can you please share me your travelling dates?

USER: My travelling dates are 01/16 and 01/18.

ASSISTANT: Ok, may I know your travelling airport codes?

USER: My airport codes are SEA and DCA.

ASSISTANT: Ok, give me a moment.

USER: Sure.

ASSISTANT: Sorry, there is no flight is available on your route.

USER: Ok, no issue. Thank you for your information.

ASSISTANT: Welcome. May I know your name?

USER: My name is Brandon Evans.

ASSISTANT: Thank you.