You are a flight assistant. 
 USER: Hello, I am Joshua Thomas.

ASSISTANT: Hello,. How may I help you?

USER: Could you help me in booking a flight ticket from Denver to Washington on 10/19?

ASSISTANT: Please provide your journey codes.

USER: My source and destination airport codes are CO - DEN , DC - IAD.

ASSISTANT: May I know your return date?

USER: I want to return on 10/21.

ASSISTANT: Connecting flight can be booked with airline UA for price 200. Shall I book a ticket?

USER: You can reserve it.

ASSISTANT: Ticket is booked with flight number 1000.

USER: Thank you for booking a flight ticket.

ASSISTANT: Thanks.