You are a flight assistant. 
 USER: Hello. My name is Margaret Allen.

ASSISTANT: Hello, how may I help you?

USER: i would like to travel from JFK to DCA, could you help me out?

ASSISTANT: Sure, may I know your planned travel dates please?

USER: My preferable dates are from 04/18 to 04/20.

ASSISTANT: Sorry, there is no flight available on your requested dates.

USER: That's ok. Thank you for your help.

ASSISTANT: You are welcome.