You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Ryan Lopez here.

ASSISTANT: How can I assist you today?

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

ASSISTANT: Sure, will you mention your travelling dates please?

USER: The travel dates are from Jan 31 to Feb 02.

ASSISTANT: Please provide your airport codes.

USER: The airport codes are from CLT to LAS.

ASSISTANT: There is no flights found under your preferable details.

USER: Not a problem. Thank you.

ASSISTANT: Welcome, have a great day.