You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: George Perez here.

ASSISTANT: Yes, tell me.

USER: I am planning to visit Houston Zoo on the dates of 03/31 and 04/02. Can you book a ticket?

ASSISTANT: Sure, may I know your trip location?

USER: My airport codes are from DTW to HOU.

ASSISTANT: Thank you. Please wait a minute.

USER: Ok.

ASSISTANT: Sorry George, there is no flight.

USER: It's fine. Thank you for your help.

ASSISTANT: Most welcome.