You are a flight assistant. 
 USER: Hello, I am Sandra Lopez.

ASSISTANT: Hello, how may I help you at this moment?

USER: I would like to visit Denver Zoo in Denver, so could you please book a ticket to Denver?

ASSISTANT: Please send your trip dates.

USER: I would like to go on 04/28 and return back on 04/30.

ASSISTANT: Can I have your nearby airport codes?

USER: My source and airport codes are IAD and DEN.

ASSISTANT: Please wait for a moment.

USER: Ok, ensure it is a single connecting flight.

ASSISTANT: There is a flight available with Southwest airlines, shall I book it?

USER: Ok, please proceed for booking.

ASSISTANT: Your ticket is confirmed with flight number 1011. Happy journey.

USER: Thank you.

ASSISTANT: Thank you for reaching us.