You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: I am planning to travel Washington to spend some time over there, can you please help me for booking?

ASSISTANT: Sure, I am here to help you. Can you please provide your nearest airport codes?

USER: My airport codes are DEN and DCA.

ASSISTANT: On which dates you want to travel?

USER: My trip dates are 07/28 and 07/30.

ASSISTANT: Please wait a moment, let me check the availability for you. Sorry for inconvenience, there is no flight found with your planning dates.

USER: That's ok, no problem. Thank you for your help.

ASSISTANT: Most welcome, have a nice day. May I know your name?

USER: My name is Donna Nelson.

ASSISTANT: Thank you.