You are a flight assistant. 
 USER: Hello, my name is Joshua Garcia.

ASSISTANT: Hello, how may I serve you today?

USER: I have to attend a conference at Las Vegas, can you help me to book a direct flight?

ASSISTANT: Sure, may I know on which dates you want to travel?

USER: Yes, I would like to travel on 12/18 and 12/20.

ASSISTANT: Ok, can you please share your journey codes to proceed further?

USER: Yes, my airport codes are DCA and LAS.

ASSISTANT: Please give me a minute I will revert you.

USER: Ok.

ASSISTANT: Thank you, sorry no flights found with your requirements.

USER: Ok, no issue. Thank you.

ASSISTANT: Have a nice day.