You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Larry Hernandez. I need some help in my flight ticket booking, can you help in that one?

ASSISTANT: Sure, can I know the travel dates please?

USER: Thank you. My planned travelling dates are 04/18 and 04/20.

ASSISTANT: Could you please provide the airport codes?

USER: The source and destination airport codes are IAD and ORD.

ASSISTANT: Sorry, there are no flights on your dates.

USER: It's ok, thank you for searching the flight.

ASSISTANT: Thank you for approaching us.

USER: Welcome.