You are a flight assistant. 
 USER: Hello, I am Joseph Lee.

ASSISTANT: Hello, how may I help you at this moment?

USER: I would like to go to a event in Washington, so could you please book a ticket for me?

ASSISTANT: Sure, I will help you. Please send your travelling dates.

USER: Sure, I would like to go on 04/06 and return back on 04/08.

ASSISTANT: Noted. Can I have your nearby airport codes?

USER: My source and destination airport codes are PHL and IAD.

ASSISTANT: Please wait for a while, I will check the availability.

USER: Ok, ensure it is a single connecting flight.

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

USER: That's ok, thank you for checking.

ASSISTANT: You are welcome, have a nice day.