You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: I am Brian Hill. I want to book a flight ticket to visit the White House in Washington, could you please help me in booking a flight ticket?

ASSISTANT: Sure, when are you willing to travel?

USER: I want to fly on 05/21 and return on 05/23.

ASSISTANT: Ok, let me know your airport codes?

USER: My source is Los Angeles, CA - LAX and destination code is DC - DCA.

ASSISTANT: Ok, any other specifications?

USER: I need a halt in between my journey.

ASSISTANT: Ok, please hold on a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, no flights found with your requested details.

USER: Not an issue. Thank you.

ASSISTANT: Thanks for choosing us.