You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I help you?

USER: I am David Hill. Can you book a direct flight for me to attend a emergency meeting in Detroit, DTW?

ASSISTANT: Sure Mr.Hill,  may I know your travelling dates?

USER: My travelling dates are, depart on 12/26 and return on 12/28.

ASSISTANT: What is your Source airport code?

USER: My source point is Denver, DEN.

ASSISTANT: Please wait, while I work on your ticket booking.

USER: Sure.

ASSISTANT: We have a UA airline direct flight number 1023 and the cost is 200. Shall I proceed?

USER: Ok, proceed.

ASSISTANT: Your booking has been done.

USER: Thanks for your help.

ASSISTANT: Thanks for approaching us.