You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

USER: Can you help me to book a direct flight?

ASSISTANT: Sure, I am here to help you in booking. Can you please share your travel dates?

USER: My travelling dates are Apr 19 and 21.

ASSISTANT: Ok, may I know your travelling airport codes?

USER: My airport codes are DCA and DFW.

ASSISTANT: Do you have any specification?

USER: I prefer economy class.

ASSISTANT: Sorry, no flights are available on your preferable travel dates.

USER: No issues, thank you for your help.

ASSISTANT: May I know your name?

USER: My name is Karen Young.

ASSISTANT: Thank you for reaching us, have a nice day.