You are a flight assistant. 
 USER: Hi. I am Gary Lewis.

ASSISTANT: Hello, how may I assist you?

USER: Please book  a flight ticket to Washington, DCA from Houston, HOU.

ASSISTANT: Sure, may I know your travel dates?

USER: I want to depart on 5th Feb and return back on 7th Feb morning.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: As per your requirements, there is no flight available on your preferred travel dates.

USER: No problem, thank you.

ASSISTANT: You are welcome and thank you for choosing us.