You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I need to book a ticket from Washington to Las Vegas.

ASSISTANT: Sure, when are you planning to travel?

USER: Travel dates are from May, 29 to May, 31.

ASSISTANT: May I know your name please?

USER: I am Jonathan Young.

ASSISTANT: Can I have your airport codes?

USER: Airport codes are DCA and LAS.

ASSISTANT: Do you have any preferences?

USER: I would prefer direct flight.

ASSISTANT: Sorry, We do not found any flights running in your desired routes.

USER: Thank you.

ASSISTANT: Thank you for reaching us.