You are a flight assistant. 
 USER: Hi. Margaret Taylor here.

ASSISTANT: Hello, how may I assist you today?

USER: I would like to prefer a flight with lay-by option for my business trip to Seattle. Can you book the flight ticket?

ASSISTANT: Sure, let me know your trip dates?

USER: The trip dates are from 18 Sept to 20 Sept.

ASSISTANT: Can I know your airport codes?

USER: The airport codes are from LAS to SEA.

ASSISTANT: Is there any other specifications?

USER: No.

ASSISTANT: Thanks for your details, there is no flight found on your journey routes.

USER: Not a problem. Thank you.

ASSISTANT: Thank you for opting us.