You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Katherine Hernandez.

ASSISTANT: How may I assist you today?

USER: I am looking to book a flight ticket from SFO to DCA to meet my friend. Can you help me for booking a flight ticket?

ASSISTANT: Sure, I will help you in booking.

USER: Thank you.

ASSISTANT: May I know when you want to travel?

USER: My travelling dates are Nov 18 and Nov 20.

ASSISTANT: Let me know your specifications.

USER: My class preferences is economy.

ASSISTANT: We are sorry to inform you that there is no flight found with your provided information.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for choosing us.

USER: Welcome.