You are a flight assistant. 
 USER: Hello.

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

USER: Could you please help me to book a business class ticket from Denver to attend my sister's marriage in Washington?

ASSISTANT: Sure, I will assist you with that. Can you please mention your preferable travel dates?

USER: I need to depart on Nov 3rd and my return date will be on Nov 5th.

ASSISTANT: May I know your preferable airport code names?

USER: My source and destination airport codes are DEN and DCA.

ASSISTANT: May I know your name for further process?

USER: I am Elizabeth Lopez.

ASSISTANT: Is there any additional preferences do you have?

USER: I need a direct flight and I want to depart in the morning.

ASSISTANT: Do you have any another specification?

USER: No.

ASSISTANT: Ok, please hold on a moment.

USER: Sure.

ASSISTANT: Sorry, no flights are available in this route as per your requested dates.

USER: No issues, I'll choose any alternative to reach my destination. Thank you.

ASSISTANT: Thank you for reaching us.