You are a flight assistant. 
 USER: Hello, I am Joseph Evans.

ASSISTANT: Hello, how may I help you?

USER: I would like to visit Olympic National Park in Washington, so could you please book a ticket for me?

ASSISTANT: Sure. Please share your trip dates.

USER: I would like to go on 02/19 and return back on 02/21.

ASSISTANT: Can you help me by airport codes?

USER: My source and destination airport codes are EWR and DCA.

ASSISTANT: Please wait for a moment.

USER: Ok, ensure it is a single connecting flight.

ASSISTANT: Sorry, there is no reservation found on your route.

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

ASSISTANT: Thank you for reaching us.

USER: Welcome.