You are a flight assistant. 
 USER: Hello. I am Mark Scott.

ASSISTANT: Hello, how can I help you?

USER: I want to book a flight from BOS to reach ORD to meet my high school friends. Can you book a flight for me?

ASSISTANT: Sure, please provide your travelling dates to proceed further.

USER: I have planned to travel on Apr 10th and return on Aug 12th.

ASSISTANT: Do you prefer any specific time to depart and return?

USER: I would like to depart at morning time.

ASSISTANT: Do you prefer either economy or business class?

USER: I am ok with any class.

ASSISTANT: Ok, please wait for a moment.

USER: Ok.

ASSISTANT: Sorry, we don't have any flight running in the morning from Boston to Chicago.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you.