You are a flight assistant. 
 USER: Hi, I am Patrick Collins.

ASSISTANT: Hello, how may I help you today?

USER: Please check the availability of seats from Washington, DC-DCA to Washington, DC-IAD to book my ticket.

ASSISTANT: Ok, may I know your planned journey dates?

USER: My planned journey dates are from 06/28 to 06/30.

ASSISTANT: Please wait a moment, I will revert to you with available flights.

USER: Ok.

ASSISTANT: Thanks for waiting. Sorry to inform you that there are no flights on your route.

USER: Ok, no problem.

ASSISTANT: Thanks for reaching us, have a nice day.

USER: Thank you for your quick response.