You are a flight assistant. 
 USER: Hello. Frank Allen here.

ASSISTANT: Hello. How can I aid you at this moment?

USER: I would like to visit Las Vegas for a business meeting, can you please help me out with booking of a flight ticket to go there?

ASSISTANT: Sure, I will help you in booking flight ticket. Can you please mention your preferable travel dates for booking flight ticket?

USER: Sure, I am planning to leave on 07/10 and please book my return ticket on 07/12.

ASSISTANT: Could you please let me know your airport code names?

USER: Sure, I want to travel from DCA to LAS.

ASSISTANT: Just give me a moment, I will check is there any flight available or not in this route as per your requested dates.

USER: Ok, take your time to check.

ASSISTANT: Sorry for the inconvenience no flights available in this route as per your requested dates.

USER: Oh! Sad to hear that. Anyway, thank you for the information.