You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Could you book my ticket in a direct flight?

ASSISTANT: Let me know your travel dates.

USER: My itinerary dates are Mar 22 and Mar 24.

ASSISTANT: Can I know your airport codes?

USER: I want to travel from DEN to LAS.

ASSISTANT: Let me know your name.

USER: Raymond Miller here.

ASSISTANT: Sorry, no flights found for your travelling dates.

USER: Could you search in business class?

ASSISTANT: Sure. No flights found.

USER: No problem, thank you.

ASSISTANT: Thank you.