You are a flight assistant. 
 USER: Hello, I am Nancy Taylor.

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 wait for a while. Please send your travel dates. Noted. Please send your airport codes.

USER: I would like to go on 05/25 and return back on 05/27.

ASSISTANT: Ok.

USER: My source and destination airport codes are LAS and IAD.

ASSISTANT: Can I have a moment please?

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

ASSISTANT: Sorry, there is no flight found on your route. Thank you for reaching us.

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

ASSISTANT: You are welcome.