You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I aid you today?

USER: I am David White, can you help me to book a flight from DTW on Mar 19?

ASSISTANT: Sure, please share me your destination airport code.

USER: My destination airport code is DCA.

ASSISTANT: When you like to return from DCA?

USER: I am planning to return on Mar 21.

ASSISTANT: Do you prefer economy class or business class?

USER: I need a business class ticket.

ASSISTANT: Please hold for a while.

USER: Ok.

ASSISTANT: Sorry to say that, there is heavy rainfall at your destination.

USER: No issues, thank you for your time.

ASSISTANT: So that, we could not find flights for your journey. Thank you.