You are a flight assistant. 
 USER: Hi.

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

USER: Can you please help me in booking from DFW to IAD?

ASSISTANT: Sure, I am here to help you with that. May I know your travelling dates, please?

USER: My travelling dates are from May 9 to May 11.

ASSISTANT: Can I know your connection limit?

USER: I need a connecting flight.

ASSISTANT: Which class do you prefer either economy or business?

USER: I am comfortable with any class.

ASSISTANT: Do you have any other specifications?

USER: I want to depart in the evening.

ASSISTANT: May I know your name for further process?

USER: My name is Thomas Williams.

ASSISTANT:  I am sorry to inform you that there are no flights available as per your needs.

USER: Ok, no issues, thanks for the information.

ASSISTANT: Thank you for reaching us, have a great day.