You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you?

USER: Donald White here.

ASSISTANT: Ok.

USER: I want to attend a Seminar in Seattle. Can you please help me for booking the flight ticket?

ASSISTANT: Sure, can I know your preferable dates?

USER: My travelling dates are from 01/10 to 01/12.

ASSISTANT: Ok, can I know your airport codes?

USER: My airport codes are from IAD to SEA.

ASSISTANT: I am sorry, there are no flights available.

USER: Anyway, thanks for the information.

ASSISTANT: Thank you, have a good day.