You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: Can you avail me to book a flight from DCA to SEA?

ASSISTANT: Do you prefer connecting flight?

USER: I need a direct flight.

ASSISTANT: Ok. Would you like to travel in economy class or business class?

USER: I am ok with any class.

ASSISTANT: Could you let me know your travelling dates?

USER: My travelling dates are Oct 19th and Oct 21st.

ASSISTANT: May I know your name?

USER: Alexander Campbell.

ASSISTANT: Sorry, currently there are no flights for your requirement.

USER: Ok, no issues. Thank you.

ASSISTANT: Thank you. Have a nice day!.