You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, good morning! How can I assist you?

USER: Can you please help me to book a direct flight to reach Denver?

ASSISTANT: Sure, I can help you with that. May I know your source and destination airport codes please?

USER: Sure, my airport codes are JFK - DEN.

ASSISTANT: Can you please provide your planned departure and return travel dates?

USER: My planned dates are on Sept 18th to 20th.

ASSISTANT: How many stop overs are you expecting in between your journey?

USER: I have already mentioned.

ASSISTANT: Please let me know if you have any other specifications, I'll search for the flights according to that.

USER: I would like to depart and return in afternoon time and also I prefer an economy class.

ASSISTANT: Can I have your good name please?

USER: Sure, my name is Michael Robinson.

ASSISTANT: Sorry to inform you that there are no flights available for you on those dates with your given details.

USER: No issues, thank you.

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