You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

USER: I am David Phillips. I want to book a flight ticket to meet my friends in Washington. Could you help me in booking a flight ticket?

ASSISTANT: Can you please share on what dates you are willing to travel?

USER: I would like to fly on 05/14 and return on 05/16.

ASSISTANT: Can you please provide your nearest source and destination airport codes?

USER: My source is Las Vegas, NV - LAS and destination is DC - IAD.

ASSISTANT: Sorry, there is no flight available on  your requested dates.

USER: Not an issue. Thank you for your service.

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