You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am Melissa Edwards want to attend a business conference at Las Vegas, can you help me to book a direct flight?

ASSISTANT: Sure, on which dates you are planned to fly?

USER: My planned dates to travel are 08/18 and 08/20.

ASSISTANT: Could you please share your airport codes?

USER: Yes, I want to fly from DFW to LAS.

ASSISTANT: Please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there is no flight is available for you.

USER: That's ok, thank you for the information.

ASSISTANT: Thank you for choosing us, have a nice day.