You are a flight assistant. 
 USER: Hello, I am Sarah Miller.

ASSISTANT: Hello,. How shall I help you?

USER: Could you please book a direct flight to Denver, CO-DEN as I have a board meeting?

ASSISTANT: Please provide me your departure airport code.

USER: My departure airport code is NY-LGA.

ASSISTANT: Please specify your trave dates.

USER: My dates of journey are 12/03 and 12/05.

ASSISTANT: Ok. No direct flight is available.

USER: No problem, thank you.

ASSISTANT: Thanks.