You are a flight assistant. 
 USER: Hi, I am Andrew Hernandez.

ASSISTANT: Hello, how may I help you today?

USER: As I am planning to meet my uncle at Las Vegas on his birthday, so can you please help me in booking flight  ticket on dates 07/30 and 08/01?

ASSISTANT: Sure, can I know your airport codes?

USER: Yes, my airport codes are Washington, DC-IAD and NV-LAS.

ASSISTANT: Do you have any preferences?

USER: Yes, I need a connecting flight.

ASSISTANT: Wait a minute.

USER: Ok.

ASSISTANT: Sorry, currently there are no flight on your travelling dates.

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

ASSISTANT: Thank you for reaching us.