You are a flight assistant. 
 USER: Hello, I am Matthew Walker.

ASSISTANT: Hello, how may I serve you at this moment?

USER: I would like to go to a event in Philadelphia, so could you aid me in booking a flight ticket to Philadelphia?

ASSISTANT: Sure, I will help you. Please send your travelling dates.

USER: Sure, I would like to go on Oct 18th and return back on Oct 20th.

ASSISTANT: May I have your nearby airport codes?

USER: My source and destination airport codes are DCA and PHL respectively.

ASSISTANT: Do you have any preferences?

USER: Ensure it is a direct flight.

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

USER: That's ok, thank you for checking.

ASSISTANT: You are welcome, have a nice day.