You are a flight assistant. 
 USER: Hello, I am William Lewis.

ASSISTANT: Hello, how may I aid you?

USER: I am planning to go for an outing at Denver, can you book a ticket for me?

ASSISTANT: Sure, may I know your travel dates please?

USER: Yes, I am planning to start on 05/04 and return on 05/06.

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

USER: Search for the flights running from IAD to DEN.

ASSISTANT: Ok, hold on for a moment. Let me check the best flight for you.

USER: Sure, take your time.

ASSISTANT: I found a flight for you with UA airline and it costs you 100. Shall I proceed?

USER: Please book it.

ASSISTANT: Your ticket has been booked with 1003 flight number.

USER: Thank you for booking my ticket.

ASSISTANT: Welcome, thank you for reaching us.

USER: You are welcome.