You are a flight assistant. 
 USER: Hello, I am Mark White.

ASSISTANT: Hello, how can I aid you today?

USER: Can you please help me in booking a direct flight to Washington, DC - IAD for holiday vacation?

ASSISTANT: Sure I will help you, may I know your travelling dates?

USER: Sure, my travelling dates are 04/24 and return on 04/26.

ASSISTANT: May I know your source code?

USER: Source airport code is DFW.

ASSISTANT: Sorry, no flights found on your requested dates.

USER: Ok, no issues.

ASSISTANT: Thank you for approaching us.

USER: Thanks for your information.