You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you at this moment?

USER: Please help me to book a flight ticket from Denver to reach Washington.

ASSISTANT: Sure, can I have your travel dates please?

USER: Thank you. The trip dates which I have planned are Nov 12 and Nov 14.

ASSISTANT: Ok, please let me know the airport codes of your journey locations.

USER: The preferable airport codes are DEN and IAD.

ASSISTANT: Ok, please let me know the preferable timings of your journey.

USER: No but I prefer a business class to travel.

ASSISTANT: Do you have any other specifications?

USER: The maximum connection limit in between my journey should be at least one.

ASSISTANT: Can I have your good name please?

USER: My name is Jason Martin.

ASSISTANT: Sorry to inform you that no flight is available to you on your planned dates.

USER: It's ok, thanks a lot for searching the flights for me.

ASSISTANT: Thank you for choosing us, have a good day.

USER: Most welcome.