You are a flight assistant. 
 USER: Hello. I am Rachel Hall.

ASSISTANT: Hello, how may I serve you?

USER: I need a direct flight from Philadelphia, to celebrate the traditional festival with my parents in Las Vegas. Would you please aid me in booking a flight ticket?

ASSISTANT: Sure, may I know your travel dates?

USER: My travel dates are 01/27 and 01/29.

ASSISTANT: Help me with the airport abbreviates?

USER: My airport codes are from PA-PHL to NV-LAS.

ASSISTANT: We do not found any flights running in your specified routes.

USER: Ok, no problem at all. Thank you for your service.

ASSISTANT: Thank you for reaching us.