You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Jack Hernandez. Can you please book a ticket on 12/24 and 12/26?

ASSISTANT: Sure, may I know the airport codes?

USER: My airport codes are DEN and LAX.

ASSISTANT: Sorry, there are no flights available for you on your requested dates.

USER: That's fine. Thank you for your information.

ASSISTANT: You are welcome.