You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Andrew Lewis. I am planning to travel to Houston for hiking with friends, so I want to book a ticket from Las Vegas.

ASSISTANT: Ok, can you please share your preferable dates to travel?

USER: I am travelling on 08/19 and return on 08/21.

ASSISTANT: May I know your source and destination airport codes?

USER: I am departing from Las Vegas-LAS and land in Houston-IAH.

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

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

ASSISTANT: You are most welcome.