You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: Please help me in booking flight ticket from IAD to DEN to meet my family.

ASSISTANT: Sure, please share me your trip dates.

USER: My trip dates are Sept 21 to Sept 23.

ASSISTANT: Do you need direct flight or connecting flight?

USER: I prefer to travel in connecting flight.

ASSISTANT: For booking, we need your good name. Please mention it.

USER: Emily Davis.

ASSISTANT: May I know your class preferences?

USER: No.

ASSISTANT: Sorry to say that, there are no flights available on the routes of your journey.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for opting us.