You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Brian White here.

ASSISTANT: How can I assist you?

USER: I want to book a flight reservation on the route from 03/09 to 03/11, can you help me out?

ASSISTANT: Sure, could you please provide me your preferred airport codes?

USER: My airport codes will be from DFW to DCA, can you help me out?

ASSISTANT: Ok, please wait for a while.

USER: Sure.

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

USER: Ok, that's completely fine. Thank you for checking.

ASSISTANT: You are welcome and thank you for contacting us.

USER: You are most welcome.