You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

USER: I am Gary Clark, can you help me to book a direct flight?

ASSISTANT: Sure, we are here to help you. May I know your airport codes?

USER: My preferred airport codes are ORD and DTW.

ASSISTANT: Please share your trip dates.

USER: My travelling dates are Mar 18 and 20.

ASSISTANT: Sorry to inform you that there is no flight for your required travel dates.

USER: No issues, thank you for your information.

ASSISTANT: Thank you for choosing us.