You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I provide assistance to you?

USER: I am very excited to meet my family after a long time, can you please help me to book a flight ticket to Las Vegas?

ASSISTANT: Sure, may I know your travelling dates?

USER: My planned dates are Aug 15 and Aug 17 respectively.

ASSISTANT: Can I know your airport codes?

USER: My airport codes are IAD and LAS.

ASSISTANT: Do you need any other specifications?

USER: I need a direct flight.

ASSISTANT: May I know your name?

USER: Myself Joseph Scott.

ASSISTANT: Sorry, there are no flights available on your travelling dates.

USER: That's fine, thank you for checking.

ASSISTANT: Thank you for choosing us.